如果您将Mac升级到 macOS 12 Monterey，但仍然遇到稳定性问题或发现新功能令人印象深刻，您始终可以选择回退到Big Sur。
您有多种方法可以将 macOS Monterey降级到Big Sur（例如，恢复较旧的 Time Machine 备份(restoring an older Time Machine backup)或使用 Internet 恢复(using Internet Recovery)）。但适用于任何兼容 Big Sur 的 Mac(Big Sur-compatible Mac)的方法包括擦除Monterey并通过可启动的USB驱动器 安装Big Sur 。
注意(Note)：如果您的MacBook Pro、MacBook Air、iMac 或Mac mini附带 macOS Monterey，则不能将其降级到Big Sur或其他版本的 macOS。
备份你的 Mac
从 macOS Monterey(Monterey)降级到Big Sur会导致数据丢失。因此，在开始之前，我们强烈建议您设置 Time Machine(setting up Time Machine)。由于来自 macOS Monterey的(Monterey)Time Machine备份与Big Sur完全兼容，因此在降级过程之后迁移数据应该没有问题。
如果您已经使用Time Machine，只需在菜单栏上选择Time Machine > Back Up Now 。如果没有，请执行以下步骤。
1. 将空的外部硬盘驱动器或SSD连接到您的Mac。理想情况下(Ideally)，它应该匹配或超过内部存储驱动器的容量。
2. 选择菜单栏上的Apple图标，然后选择(Apple)系统偏好设置(System Preferences)>时间机器(Time Machine)。
3. 选择选择备份磁盘(Select Backup Disk)按钮。
4. 选择外部驱动器并选择使用磁盘(Use Disk)。
5. 等到Time Machine格式化并将您的(Time Machine)Mac备份到外部驱动器。
或者，您可以在开始之前手动将任何重要文件和文件夹复制到外部驱动器。如果您没有备用外部设备，请尝试将文件上传到 iCloud Drive(uploading your files to iCloud Drive)（如果您使用Apple ID登录）或其他有足够可用空间的云存储服务。
下载 macOS Big Sur 安装程序
备份您的Mac后，您必须通过App Store下载 macOS (App Store)Big Sur安装程序。它的重量为 12 GB，因此需要等待 1-2 小时才能完成下载。
1. 选择以下链接，打开Mac App Store的 macOS (Mac App Store)Big Sur下载页面。如果您不使用Safari，请在选择链接后选择打开 App Store 。( Open App Store )
下载 macOS 11 大苏尔(Download macOS 11 Big Sur)
2. 选择获取(Get )按钮。
3. 选择下载(Download)将Big Sur安装程序下载到 Mac 的应用程序(Applications)文件夹中。
4. 一旦您的Mac完成下载Big Sur安装程序，它将尝试启动安装程序 - 选择退出(Quit)或按Command + Q退出它。
格式化闪存驱动器
接下来，您必须将注意力集中在创建可启动的 macOS Big Sur USB上。为此，您需要一个存储容量至少为 16GB 的空闪存驱动器。然后您必须在Mac OS 扩展文件系统(Mac OS Extended file system)中对其进行格式化。
1. 将闪存驱动器连接到您的Mac。
2. 打开启动板并选择其他(Other)>磁盘工具(Disk Utility)。
3. 按住 Control 键单击磁盘工具(Disk Utility)侧栏上的闪存驱动器，然后选择擦除(Erase)。
4. 输入驱动器名称并将格式设置为Mac OS Extended (Journaled)。然后，再次选择擦除(Erase)。
5.等待(Wait)磁盘工具(Disk Utility)完成驱动器格式化。
6. 选择完成(Done)并退出磁盘工具。
创建可启动的 Big Sur USB
完成驱动器格式化后，您必须使用 Mac 的终端(use the Mac’s Terminal)创建可引导的Big Sur USB 。
1. 打开 Launchpad 并选择其他(Other)>终端(Terminal)。
2. 在终端(Terminal)窗口中输入以下命令，将drive_name替换为闪存驱动器的名称：
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia –volume /Volumes/drive_name
3. 按回车(Enter)。您需要管理员密码，因此请输入并再次按Enter 键(Enter)。
4. 键入Y确认您要擦除闪存驱动器。如果您看到一条弹出消息，要求您提供终端(Terminal)权限以访问闪存驱动器，请选择确定(OK)。
5.等到(Wait)终端(Terminal)完成创建可引导的Big Sur USB。看到Install media now available后退出它。
在 T2 Mac 上启用外部引导
如果您使用内置 Apple T2 安全芯片的 Intel Mac，则(Intel Mac with an Apple T2 Security Chip)必须激活允许通过 macOS恢复(Recovery)从外部媒体启动的特定设置。这不适用于在Apple Silicon上运行的 macOS 设备（例如M1 Macs）。
1. 打开Apple菜单并选择重新启动(Restart)。
2. 按住Command和R键并再次选择重新启动(Restart)。一直按住直到看到Apple标志。macOS恢复(Recovery)将立即显示。
3.在菜单栏上选择实用程序(Utilities)>启动安全实用程序。(Startup Security Utility)
4. 选择输入 macOS 密码(Enter macOS Password)并输入您的管理员密码。此外，输入 Mac 的固件密码（如果需要）。
5. 选择允许从外部或可移动媒体启动(Allow booting from external or removable media)旁边的单选按钮。
注意：如果您稍后安装 macOS (Note)Big Sur时遇到问题，请重新访问此屏幕并将Secure Boot设置为Medium Security或No Security。
6. 退出启动安全实用程序(Startup Security Utility)。
7. 打开Apple菜单并选择关机(Shut Down)。
从闪存驱动器启动
您现在必须从USB驱动器启动您的(USB)Mac才能进入Big Sur的macOS恢复(Recovery)。但是，该过程会略有不同，具体取决于您使用的是Intel Mac 还是 Apple Silicon Mac(Intel Mac or an Apple Silicon Mac)。
重要提示(Important)：如果您使用带有Apple T2 安全芯片的(Apple T2 Security Chip)Intel Mac，请确保在继续之前使用上述说明启用从外部媒体启动。
英特尔 Mac(Intel Macs)
1. 关闭你的 Mac。
2.按住Option键再开机，进入开机选择画面。
3. 选择 macOS Big Sur可启动USB并选择Continue。
苹果硅 Mac(Apple Silicon Macs)
1. 关闭你的 Mac。
2. 按住电源(Power)按钮将其重新打开。看到Loading startup options 消息(Loading startup options message)后释放。
3. 选择 macOS Big Sur可启动USB并选择Continue。
抹掉 macOS Monterey
在 macOS Recovery for Big Sur中，您必须使用磁盘工具(Disk Utility)来擦除 Mac 的内部存储数据(erase Mac’s internal storage data)。如果您还没有，这是您退出恢复模式(Recovery Mode)并创建文件备份的最后机会。
1.在 macOS 恢复菜单上选择磁盘工具(Disk Utility)>继续。(Continue)
2. 在边栏上选择Macintosh HD并选择Erase。
3. 保持默认名称和格式——Macintosh HD和APFS——完整。
4. 再次选择擦除(Erase)以确认。如果您看到“擦除卷组”(Erase Volume Group)按钮，请改为选择该按钮。
5. 选择完成(Done)。
6. 退出磁盘工具（在菜单栏上选择磁盘工具(Disk Utility)>退出磁盘工具）。(Exit Disk Utility)您的Mac应该恢复到 macOS恢复(Recovery)菜单。
安装 macOS Big Sur
您现在可以在Mac上安装 macOS (Mac)Big Sur。
1.在 macOS恢复(Recovery)Big Sur菜单上选择重新安装 macOS Big Sur(Reinstall macOS Big Sur) >继续。(Continue)
2.在 macOS Big Sur 安装程序上选择继续。(Continue)
3. 同意许可条款并选择Macintosh HD作为安装目的地。然后，选择继续(Continue)并按照屏幕上的所有说明安装操作系统。
设置 Big Sur 并迁移数据
安装 macOS Big Sur后，您的Mac可能会要求您连接到互联网，以便它能够自行激活。使用有线连接或选择屏幕左上角的 Wi-Fi图标以加入 Wi-Fi 热点。(Wi-Fi )
之后，您将遇到设置助手(Setup Assistant)。选择您所在的国家或地区，然后按照屏幕上的说明在您的(Select)Mac上设置新的 macOS Big Sur副本。
如果您使用 Time Machine，请选择从 Mac、Time Machine 备份或启动磁盘选项以从(From a Mac, Time Machine backup, or Startup disk)Time Machine备份 恢复。
或者，您可以在完成Mac设置后恢复数据。为此，请打开Launchpad并选择Other > Migration Assistant。
macOS Monterey到Big Sur 降级完成(Big Sur Downgrade Complete)
上面的说明应该已经帮助您从 macOS Monterey(Monterey)成功降级到Big Sur。如果您想稍后升级到Monterey，只需打开Apple菜单并选择System Preferences > Software Update > Upgrade Now即可。同时，不要忘记通过软件更新(Software Update)工具应用任何Big Sur积分更新。
How to Downgrade From macOS Monterey to Big Sur
Іf you upgraded your Mаc to macOS 12 Monterey but keep experiencing stability issues or find the nеw features underwhelming, you always have thе oрtion of falling back to Big Sur.
You’ve got multiple ways to downgrade macOS Monterey to Big Sur (e.g., restoring an older Time Machine backup or using Internet Recovery). But the method that works on any Big Sur-compatible Mac involves erasing Monterey and installing Big Sur via a bootable USB drive.
Note: If your MacBook Pro, MacBook Air, iMac, or Mac mini shipped with macOS Monterey, you can’t downgrade it to Big Sur or another version of macOS.
Back Up Your Mac
Downgrading from macOS Monterey to Big Sur will result in data loss. So before you begin, we strongly recommend setting up Time Machine. Since Time Machine backups from macOS Monterey are fully compatible with Big Sur, you should have no trouble migrating your data after the downgrade process.
If you already use Time Machine, just select Time Machine > Back Up Now on the menu bar. If not, go through the steps below.
1. Connect an empty external hard drive or SSD to your Mac. Ideally, it should match or exceed the capacity of the internal storage drive.
2. Select the Apple icon on the menu bar and choose System Preferences > Time Machine.
3. Pick the Select Backup Disk button.
4. Choose the external drive and select Use Disk.
5. Wait until Time Machine formats and backs up your Mac to the external drive.
Alternatively, you can copy any important files and folders to an external drive manually before you begin. If you don’t have a spare external device, try uploading your files to iCloud Drive (if you’re signed in with an Apple ID) or another cloud storage service with sufficient free space.
Download macOS Big Sur Installer
After backing up your Mac, you must download the macOS Big Sur installer via the App Store. It weighs in at 12 GB, so expect to wait for 1-2 hours until the download finishes.
1. Select the link below to open the macOS Big Sur download page on the Mac App Store. If you don’t use Safari, select Open App Store after selecting the link.
Download macOS 11 Big Sur
2. Select the Get button.
3. Select Download to download the Big Sur installer to your Mac’s Applications folder.
4. Once your Mac finishes downloading the Big Sur installer, it will attempt to launch the installer—select Quit or press Command + Q to exit it.
Format the Flash Drive
Next, you must focus your attention on creating a bootable macOS Big Sur USB. For that, you need an empty flash drive with a storage capacity of at least 16GB. You must then format it in the Mac OS Extended file system.
1. Connect the flash drive to your Mac.
2. Open the Launchpad and select Other > Disk Utility.
3. Control-click the flash drive on the Disk Utility sidebar and choose Erase.
4. Enter a name for the drive and set the format to Mac OS Extended (Journaled). Then, select Erase again.
5. Wait until Disk Utility finishes formatting the drive.
6. Select Done and exit Disk Utility.
Create Bootable Big Sur USB
You must use the Mac’s Terminal to create the bootable Big Sur USB now that you’ve finished formatting the drive.
1. Open the Launchpad and select Other > Terminal.
2. Enter the following command into the Terminal window, replacing drive_name with the name of the flash drive:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia –volume /Volumes/drive_name
3. Press Enter. You need an administrator password, so type it in and press Enter again.
4. Type Y to confirm you want to erase the flash drive. If you see a pop-up message asking you to provide Terminal permissions to access the flash drive, select OK.
5. Wait until Terminal finishes creating the bootable Big Sur USB. Exit it once you see Install media now available.
Enable External Booting on T2 Macs
If you use an Intel Mac with an Apple T2 Security Chip inside, you must activate a specific setting that allows booting from external media via macOS Recovery. This does not apply to macOS devices running on Apple Silicon (e.g., M1 Macs).
1. Open the Apple menu and select Restart.
2. Hold down the Command and R keys and select Restart again. Keep holding until you see the Apple logo. macOS Recovery will show up momentarily.
3. Select Utilities > Startup Security Utility on the menu bar.
4. Select Enter macOS Password and enter your administrator password. Also, enter your Mac’s firmware password (if required).
5. Select the radio button next to Allow booting from external or removable media.
Note: If you have trouble installing macOS Big Sur later, re-visit this screen and set Secure Boot to Medium Security or No Security.
6. Exit the Startup Security Utility.
7. Open the Apple menu and select Shut Down.
Boot From the Flash Drive
You must now boot your Mac from the USB drive to enter macOS Recovery for Big Sur. However, the process slightly differs depending on whether you use an Intel Mac or an Apple Silicon Mac.
Important: If you use an Intel Mac with an Apple T2 Security Chip, make sure to enable booting from external media using the above instructions before you go ahead.
Intel Macs
1. Shut down your Mac.
2. Hold down the Option key and turn it back on to enter the boot selection screen.
3. Choose the macOS Big Sur bootable USB and select Continue.
Apple Silicon Macs
1. Shut down your Mac.
2. Turn it back on while holding down the Power button. Release once you see the Loading startup options message.
3. Choose the macOS Big Sur bootable USB and select Continue.
Erase macOS Monterey
In macOS Recovery for Big Sur, you must use Disk Utility to erase Mac’s internal storage data. If you haven’t already, this is your last chance to exit Recovery Mode and create a backup of your files.
1. Select Disk Utility > Continue on the macOS Recovery menu.
2. Choose Macintosh HD on the sidebar and select Erase.
3. Keep the default name and format—Macintosh HD and APFS—intact.
4. Select Erase again to confirm. If you see an Erase Volume Group button, select that instead.
5. Select Done.
6. Quit Disk Utility (select Disk Utility > Exit Disk Utility on the menu bar). Your Mac should revert to the macOS Recovery menu.
Install macOS Big Sur
You can now install macOS Big Sur on your Mac.
1. Select Reinstall macOS Big Sur > Continue on the macOS Recovery for Big Sur menu.
2. Select Continue on the macOS Big Sur installer.
3. Agree to the license terms and select Macintosh HD as the installation destination. Then, select Continue and follow all onscreen instructions to install the operating system.
Setup Big Sur & Migrate Data
After installing macOS Big Sur, your Mac may ask you to connect to the internet so that it can activate itself. Use a wired connection or select the Wi-Fi icon at the top-left of the screen to join a Wi-Fi hotspot.
Following that, you will come across the Setup Assistant. Select your country or region and work your way through the onscreen instructions to set up the new macOS Big Sur copy on your Mac.
If you use Time Machine, select the From a Mac, Time Machine backup, or Startup disk option to restore from Time Machine backup.
Or, you can restore your data after you’ve finished setting up your Mac. To do that, open the Launchpad and select Other > Migration Assistant.
macOS Monterey to Big Sur Downgrade Complete
The instructions above should’ve helped you successfully downgrade from macOS Monterey to Big Sur. If you want to make the upgrade to Monterey at a later time, just open the Apple menu and select System Preferences > Software Update > Upgrade Now. In the meantime, don’t forget to apply any Big Sur point updates via the Software Update tool.
