is it possible to load static library (.lib) compiled in c++ using NETLink or similar in Mathematica?
Such a library is not meant for dynamic loading and typically will not contain all of the information necessary to properly link it at runtime. It also may not contain relocatable code. If you want something that is loadable at runtime, the most straightforward approach is probably to write the code for a corresponding dynamic library (.dll file) and link this (statically) with the existing library.
So, to put it simply, the answer to your question is "no".