Can i initiate visitor visa(B2) to my mother when i am in H1B extension? I am still waiting for extension approval.

You do not initiate the visa process. Your mother must apply for a visitor visa. She starts the process by completing a DS-160. Whether she will be issued he requested visa will depend upon the reason for her trip and her ties to her native country. You can read more about visitor visas at http://myattorneyusa.com/visiting-the-usa-on-visa-waiver-program-vwp-and-b2-visas.