网上找来找去都是SQL Server 2008版本或者以前版本的。。。

后来：http://stackoverflow.com/questions/349668/removing-the-remembered-login-and-password-list-in-sql-server-management-studio

找到了更多版本的解决方案：

Another answer here also mentions since 2012 you can remove Remove cached login via How to remove cached server names from the Connect to Server dialog?. Just confirmed this delete in MRU list works fine in 2016.

SQL Server Management Studio 2016 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\13.0\SqlStudio.bin

SQL Server Management Studio 2014 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\12.0\SqlStudio.bin

SQL Server Management Studio 2012 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\11.0\SqlStudio.bin

SQL Server Management Studio 2008 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\Microsoft SQL Server\100\Tools\Shell\SqlStudio.bin

SQL Server Management Studio 2005 delete the file – same as above answer but the Vista path. C:\Users\%username%\AppData\Roaming\Microsoft\Microsoft SQL Server\90\Tools\Shell\mru.dat

These are profile paths for Vista / 7 / 8.

EDIT:

Note, AppData is a hidden folder. You need to show hidden folders in explorer.