I want to pursue M.A in psychology..But I have done my graduation in science? How can I pursue masters without doing bachelor's ?

You can surely do yourypg in psychology. I think it will be even advantage for you to have b.sc degree. In the psychology subject many terms related with science used.

There ar evaruous regular masters college for Arts like St Stephen College, Gargi College, HansarajbCollege under Delhi University.

Studnets with Literature or Arts backgrounds generally ar eligible for MA Psychology.

However for Bsc students, they can tak eup Onljne Courses Certification short term into Psychology via platform ljke Cojrsera and Edx which jave international collaboration with foreign University and are of high value.