When using Putty to connect to the router using telnet protocols, and then I pressed Enter key, there were two carriage returns in the text, how do I get rid of one of them?
I am not sure but here for you to try.
PuTTY may add one more "CR" when it see "LF", that the cause of double "CR" chars.
Look your configuration at "PuTTY\Terminal\Implicit CR in every LF"
Others have stated that the "Implicit LF with CR" and Implicit CR with LF" ONLY control how PuTTY interprets what is coming IN. An IMPLICIT CR or LF wouldn't have much value down the wire. A command for an EXPLICIT CR or LF would be handy, but that doesn't seem to be available.