I am having H1B from one employer A, Can a employer B also apply for my H1B?

You mean a transfer?

You mean a transfer?

No not transfer, rt now I am working with A. If I go for new H1B from company B, I am planning like if I will get new H1B from B, I will join that company.
So is it possible to file for a completely new H1B frm different company when you are already having H1B from other company?

If you already are on H-1, you just file for a transfer... no need to obtain a new H-1.