What if this happenens?

Question

Pokemon A uses taunt on Pokemon B. Pokemon B uses drain punch will it work

Answer 1

Yes, it will. Taunt only works on non-attacking moves, and Drain Punch is a attacking move. Also, the HP will be restored.
Source: Expierence

Answer 2

Of course. Why wouldnt it?
taunt allows you to only use attacking moves and drain punch is an attacking move.
Source: knowledge and personal experience