Hi You are trying to link dynamically a statically compiled library (this is clearly stated in the error message). The easiest way is to link statically pjsua library. regards Bogdan ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- I have problems with pjsua2.lib .I want to build project in QT.after attached all libs the project didn't build and have some error such az {pjsua2-lib-i386-Win32-vc8-Debug.lib(endpoint.obj):-1: error: LNK2038: mismatch detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value 'MDd_DynamicDebug' in main.obj} Please help me .i am a new programmer in C++ and QT.