Is there a way to share animations with different proportion models whish have same hierarchy?
for example, we have a “Man” model and a “Boy” model, they have same hierarchy, but “Man” is bigger than “boy”
If we use “Man” animations on “boy”, “boy” will be stretched.
So is there a way to only use “man” animation’s rotation data base on “boy” 's rig, and keep “boy” proportion?
Yes, what you are looking for is a rig animation retargeting solution.
Softimage began including this feature through MOTOR some years ago. Maya also has this feature now.
This is something that needs to be planned and implemented all the way from your 3d animation package. I don’t think you will be able to do this easily, if at all, from within Unity. Remember that Unity is simply reading animation data from your FBX files. It’s in your 3d package that you have to prepare rigs and plan them for recycling animations, rigs, clips, etc. It’s an entire production process really, especially for games, you want to recycle as much work as possible in order to develop more efficiently.
What animation package are you working with?
Basically we use 3dMAX, and MotionBuilder as well. we can retarget the aniamtion in the MB, but that will crease the clips either. It will be better to find some solution in the Unity.
(In Unreal animation editor, we can check “bRotationOnly” box to do this)
Might be possible to do something similar in Unity, but you would need to do some heavy scripting to do this for an entire character.
Why not set up an efficient character pipe with 3dsMax and Motion Builder; reuse and recycle most of your common animations; i.e. walk, run, jumping, attacking, etc.? If you already have animations, and you’re using a pipeline with 3dsMax and MB, why not retarget and export to Unity everything you need?
You have to remember that Unity isn’t setup for this. Unity offers a very clean and empty slate for working on games. It doesn’t include as comprehensive and prebuilt character workflow tools like UnrealEngine does. Basically, if you want the character editor, etc. from UE, it will need to be created by your in-house tool development team from scratch, as Unity doesnt provide an out of the box solution for this. So in some cases, setting up and planning an efficient character pipeline from the start would prob be best for your project. This is just my opinion though, so feel free to work on a character system in Unity that fits your project needs if you feel that would work out better.
P.S.
What do you mean by “creasing clips”?
Sorry, should be “increase”, not “crease” 
Ah, makes sense now. I wouldn’t worry about making more clips, it won’t really have an adverse effect on your project. Is the problem more with managing more animation clips in your pipeline? If you’re afraid Unity will slow down or something, it won’t.
I see. Thanks a lot