I'm doing by b.e 6th sem now when should i take up the entrance test for mba so tat i dont loose a year. Pls any1 help me

It is not the question of losing one year. The bottom line is, you have to get into a reputed B School. There are close to 2000 B Schools, in India. If you purely want to do your MBA, the options are numerous. If you are serious about your career, you need to identify some reputed B Schools, get to

You need to complete your graduation and then give the entrance test perhaps later in the same year.