Sir my wbjee rank is 18k and SC rank is 661 . Can get admission in government college?

Yes according to your rank and category you will get government College. Fill all the government Colleges before any private college in the counseling process. Fill the choices as per your desired branch. Focus on sc category seats in choice filling. Don't forget to fill Jalpaiguri Government Engineering College and Purulia Government Engineering College because there is more chance of getting admission  in these two colleges as per your rank. Do counseling properly.
Read this article Wbjee Counseling Process 2018 .