Question

Whats the command to make only ops to set topic in my Channel?

Answer 1

Only opped (+o) users may set the topic.

Note: When +t is set, only channel operators may modify the topic of the channel. This mode is recommended in larger, more public channels to protect the integrity of the topic

 

/mode #channel +t

Answer 2

You should also lock the topic in your channel.  Further info can be found on this thread:

 http://librairc.net/faq/112/how-do-i-lock-my-topic-in-channel