I have applied for H1b transfer to company B and it is still under process . But now due to some reasons I don't want to change my job to Company B.

I prefer to work with my present company. Please let me know if I can continue with my current job.

If company B's H1b gets approved , will it affect company A's approval which I am currently working ?

What should i do to cancel my approval from company B? or Can i continue without cancelling thinking of the fact that i may join B at anytime after 1 or 2 years?

You should consult your attorney...