I need to replace floor under tub , so I need to remove tub without damaging anything. I can't get the drain out, any suggestions

What kind of tub do you have? Cast iron, steel or plastic? Do you mean you can't get to the trap to unhook it? If so then why not? Once the trap is unhooked you will have to remove the drywall from the end without the faucet and any screws that nay be securing the tub to the far wall. Once everything's clear you can lift the tub up and walk it out.
I have given you directions for the most difficult which is the cast iron tub but in general it works for all tubs. Good luck, Tom

If the tub sits on raised foundation, and you have to replace sub floor, than crawl in the crawl space and disconnect drain from under neath. If your tub sits on concrete slab, than, generally speaking, there is no "floor", and tub sits directly on concrete. However, if you still have a need to remove the tub positioned on concrete slab than there should be an access door behind the tub, usually hidden inside the closet. That access hole is there to disconnect plumbing from the tub. If there is no access door than cut the wall approximately 14" x 14" ( directly behind the tub and under the tub faucet) , and snap in a plastic access door once your work is finished. If cut square, no patching or painting will be required.

Hope that helps.

Milo

The first thing I would try is a tub drain removal tool (see image). There are a number of different kinds available, but if the drain outlet has a CROSS in the drain you should be able to remove it with a basic tub drain removal tool available at home depot or lowes home improvement store(s).

Back to you...

Mark