内容来源：https://www.engadget.com/2285099/why-turn-off-phone-remove-sim-card-explained/

内容总结：

更换SIM卡不必关机，但建议关机操作。虽然如今多数智能手机支持开机状态下更换SIM卡，但关机操作仅需几秒，却能有效降低出现软件故障的概率，花几分钟换取安心是值得的。

关于实体SIM卡的更换流程，用户需手动取出卡片。具体步骤为：可选择关机或开启飞行模式；用取卡针轻推卡托弹出孔取出卡托；更换为正确尺寸的SIM卡；将卡托推回原位；按提示输入PIN码或重启手机。若使用支持双实体卡的双卡手机，更换前需确认要更换的是哪张卡。相比之下，eSIM的更换更为简便，可通过二维码、运营商应用或设备间直接转移完成，多数兼容eSIM的手机可存储多个eSIM配置文件，但同时仅能激活少数几个。

更换SIM卡的主要潜在风险多为物理层面的问题，例如灰尘或湿气进入卡托、卡片尺寸不符强行插入、卡托损坏导致对位不准，或卡片本身受损。受损或插入不当的SIM卡可能导致手机反复尝试建立网络连接而失败，进而耗电并引起过热。多数人不会遇到这些问题，只要操作时放慢速度、小心谨慎即可。通常情况下，手机读取新卡并搜索网络只需片刻，随后即可使用，具体取决于账户设置要求。

关机换卡的好处虽然有限，但确实存在：重启后手机将强制读取新卡上的信息，更快注册到新网络，从而降低出现软件层面“网络错误”提示的概率。2010年代以前，SIM卡槽通常位于可拆卸电池下方，必须关机才能操作。随着不可拆卸电池普及，卡托被移至机身外部，早期机型开机换卡常报网络错误，但很快便支持了热插拔。若不希望完全关机，开启飞行模式等待30秒后再换卡、换完后关闭飞行模式，同样可达到刷新运营商设置的效果，避免换卡过程中出现运营商相关的故障。

需要特别提醒的是microSD卡的处理。部分安卓设备仍保留microSD卡槽，有时与SIM卡共用卡托。此类情况下，取出SIM卡前必须先卸载microSD卡，以防数据丢失。以三星设备为例：打开“我的文件”应用，找到SD卡，点击旁边的三点菜单并选择“卸载”。若不确定具体操作方式，可搜索设置应用或查阅在线文档。

综上，关机更换SIM卡虽收益不大，但可预防软件层面的小故障。若不愿关机，可用飞行模式替代。换卡后如遇网络错误，应首先尝试重启设备。

中文翻译：

更换SIM卡时不必关机（但最好还是关掉）

一个简单的步骤就能消除出错的微小可能，免得之后还要花更多时间处理。

如果你的手机有SIM卡托，你可能不常打开它，但仍有需要打开的时候。你可能为了省钱而转用虚拟运营商，或者出国旅行时临时把平时的SIM卡换成更便宜的当地运营商卡。某些情况下，如果卡损坏了，运营商会给你寄一张替换卡。

如今大多数智能手机都支持开机状态下更换SIM卡，所以换卡时不需要关机。但关机确实有少许好处，而且操作如此简单，如果你有几分钟时间，稳妥一点总没错。

如何更换SIM卡

这里说的是实体SIM卡，需要你手动从手机中取出。eSIM的更换应该只需使用二维码、运营商应用或在不同的智能手机之间直接转移即可。大多数兼容eSIM的手机可以存储多个eSIM，但同一时间只能有几个处于激活状态。

实体SIM卡更换包括以下步骤：

• 可选操作：关闭手机电源或开启飞行模式。
• 弹出卡托，通常是用回形针或取卡针轻轻插入手机上的弹出孔。
• 更换卡片，确保使用正确的卡尺寸。
• 将卡托推回原位。
• 输入PIN码，或按手机提示重启。

如果你使用的是支持两张实体卡的双卡手机，换卡前先确认你要更换的是哪张SIM卡。

虽然很多人认为eSIM是更先进的技术，因为它没有活动部件，但也有人仍然看重实体SIM卡带来的便利和相对更好的隐私保护。例如，实体SIM卡让人可以轻松安装和使用柜台购买的预付费SIM卡账户。

更换SIM卡的少量潜在风险

更换SIM卡的大多数潜在危险都是物理层面的。你可能不小心让灰尘、污垢或水汽进入卡托，或者错误地把较大的卡强行插入较小的卡槽。你也可能弄坏卡托导致其无法正确对齐，或以其他方式损坏卡片。损坏的SIM卡或插入不当的卡可能导致手机持续尝试（并失败地）建立网络连接，从而消耗电池电量并导致手机过热。

大多数人从不会遇到这些问题，因为放慢速度、小心操作就能避免。大多数情况下，手机需要片刻时间来读取新SIM卡并搜索网络。之后就可以正常使用了，前提是满足账户设置要求。

换卡前关机的益处不大。关机可以迫使手机在重新开机时读取新卡上的最新信息，通过读取新的运营商设置帮助设备更快地在新网络上完成注册。这降低了换卡时遇到基于软件的“网络错误”提示的概率。

换SIM卡时还需要考虑的几点

2010年代之前，SIM卡槽通常位于手机可拆卸电池的下方，显然需要关机才能接触到。随着时间推移，可拆卸电池越来越少，SIM卡托被移到了手机外侧。早期采用这种设计的机型在开机状态下换卡时经常显示网络错误，但很快它们就支持了热插拔，这不再是个问题。

你甚至不需要完全关机就能让手机刷新卡上的运营商设置。开启飞行模式、等待30秒后再换卡、插入新SIM卡后关闭飞行模式，也能得到类似的效果。这应该能防止换卡过程中出现运营商相关的故障。

关于SD卡的提醒

与iPhone不同，一些安卓设备仍然配有microSD卡槽。某些情况下，它与SIM卡在同一个卡托中，但位置各有不同。如果你的手机是这样，那么在取出SIM卡之前，就像弹出外接硬盘一样，务必先卸载microSD卡以防止数据丢失。在三星设备上：打开“我的文件”应用，找到SD卡，点击旁边的三点菜单，选择“卸载”。如果不确定你的设备如何操作，可以在设置应用中搜索或查阅在线文档。

所以，虽然好处不大，但更换SIM卡时关机可以防止软件相关的故障。如果你不想关机，可以用飞行模式代替。另外，如果换卡后遇到网络错误，务必先尝试重启设备。

英文来源：

You don't have to turn off your phone to switch SIM cards (but you probably should)
A quick step removes the small chance of anything going wrong and requiring more of your time.
If your phone has a SIM tray, it's not something you likely open often, but there are still reasons to. You may be switching to an MVNO to save money, or maybe you're temporarily swapping out your normal SIM for a cheaper local carrier when travelling. In some cases, your carrier will send you a replacement card if yours is damaged.
Most of today's smartphones let you switch SIMs with the phone on, so you don't need to switch your device off for the process. But there are modest benefits if you do, and for something so quick, it's better to be safe if you have a few minutes.
How to replace the SIM
We're talking about physical SIM cards, which you have to remove from your phone by hand. eSIM replacement should be as simple as using a QR code, carrier app or direct transfer between different smartphones. Most eSIM-compatible phones can store many eSIMS, though only a few can be active at once.
Physical SIM card replacement involves these steps:

• Optionally, power down your phone or enable airplane mode.
• Pop the tray out, usually by gently pushing a paperclip or SIM ejector tool into the ejection pinhole on the phone.
• Change the card, ensuring you use the correct card size.
• Pop the tray back into place.
• Enter your PIN or restart if the phone requests it.
  If you have a dual-SIM phone that supports two physical cards, check which SIM you intend to swap before you begin.
  While many argue eSIM is a superior technology because it requires no moving parts, others still appreciate the convenience and relative privacy true SIM cards provide. They make it easy to install and use over-the-counter pay-as-you-go SIM-based accounts, for example.
  The small potential risks of SIM replacement
  Most potential dangers of SIM replacement are physical. You might accidentally insert dirt, grime or moisture into the SIM tray, or force a larger card into a smaller slot incorrectly. You could also break the SIM tray so it no longer aligns correctly, or otherwise harm the card. A damaged SIM card or one incorrectly inserted may cause the phone to continue trying (and failing) to create a network connection, draining its battery and causing it to overheat.
  Most people never encounter these problems, since slowing down and being careful does the trick. In most cases, your phone will take a moment to read the new SIM and find the network. Then it will be available for service, subject to account setup requirements.
  The benefit of turning your phone off before swapping the SIM is minor. It forces your phone to look at the fresh information provided on the new card when it powers on again, helping register your device on its new network more quickly by reading the new carrier settings. This reduces the chance you'll encounter a software-based "network error" message when you swap.
  More to think about when swapping SIMs
  Before the 2010s, SIM slots were usually located underneath a phone's removable battery, which obviously required powering off the device to access. Over time, as removable batteries became less common, SIM trays were moved to the outside of phones. Early models using this setup would often show a network error if you swapped SIMs while the phone was on, but they quickly became hot-swappable and this was no longer a problem.
  You don't even need to switch your device off completely to make the phone refresh its carrier settings from the card. You'll get a similar result if you turn on airplane mode, wait 30 seconds before swapping the SIM and turn airplane mode off again once the new SIM is inserted. This should prevent any carrier hiccups during the process.
  A warning on SD cards
  Unlike the iPhone, some Android devices still include a microSD card slot. In some cases, this is in the same tray as the SIM, though placement varies. If this is the case for you, as when ejecting an external drive, it's important to unmount the microSD card before removing the SIM to prevent losing data. On Samsung devices: open the My Files app, find the SD Card, tap the three-dot menu next to it and choose Unmount. Search the Settings app or check online documentation if you're not sure how this works for your device.
  So while the benefits are slight, switching off your phone when replacing the SIM can prevent software-related glitches. If you don't want to power down, use airplane mode instead. And in case you encounter a network error after swapping, always try restarting your device first.