i am in BSC 2nd year with chemistry .can i apply for GATE after completing my BSC? what is the eligibility for GATE?

You complete BSC and then MSc and then plan GATE.

no......... masters or 4 year degree

Actualy you are not eligible to write GATE,here is a eligibility criteria Candidates with B.Tech/B.E./ B.Arch/ B.Pharma (4 years after 10+2) and those who are in the final or pre-final year of such programmes are eligible to appear for GATE 2009. Those with a Master degree in any branch of Science