OK. I solved this issue. This is a subsurf modifier with armature modifier.
But i am tried several other files with skeleton and animation.
Please explain how animate it in blender. When i animating in blender already is ok. But in imported SMD animation is wrong in several bones. Only legs are working, but no neck, shoulders, arms, etc. I am using model from MakeHuman program.

Can you tell me how animate in blender correctly?

I am trying to export (and import) model to SMD format. Target engine is Source.
My blend file: http://pasteall.org/blend/index.php?id=45891
Blender version: 2.78c
BleST version: 2.9.1

In blender all is good. But when i exporting to SMD (default parameters, Source Engine), and importing it (default parameters) again to Blender i am getting some model face deformations. Can you test it? Or explain what i am doing wrong please.