The status quo described
In the afternoon, I found that the connection between my Xshell and the server node was inexplicably broken. After checking the system log, I found a large number of following errors:

May 15 17:58:08 yanta sshd[15213]： error：key_read: uudecode AAAAB3NzaC1yc2...........

The solution
After querying the solution on the network, it is found that the IP in error and the string in the corresponding error message can be found in the file /root/.ssh/known_hosts, and it is ok to delete it
. However, after checking the information on the server again, it is found that there is no corresponding one, and the encoded string is completely different.
After looking at /root/.ssh/authorized_keys, I find that one of the keys is consistent with the error message, so I first backup the file:

# cp authorized_keys authorized_keys.bk

After careful examination of the key, it was found that a complete key was originally divided into several parts, leading to the incomplete key when SSH login, so there was no error message after re-copying and pasting the key information on this machine.