The　vibration　response　characteristic　caused　by　the　change　of　gear　meshing　stiffness,　friction,　tooth　backlash　and　so　on　is　an　important　basis　for　fault　diagnosis.　In　view　of　the　situation　that　friction,　tooth　backlash　and　crack　morphology　are　considered　insufficiently,　an　analysis　method　of　gear　crack　fault　vibration　response　was　proposed　based　on　the　mathematical　model　of　time-varying　mesh　stiffness　and　virtual　prototype　technology.　The　mathematical　model　of　normal　gear　meshing　stiffness　was　solved　by　energy　method,　and　then　the　time-varying　meshing　stiffness　has　been　used　as　the　excitation　function　to　the　virtual　prototype　simulation　model,　at　the　same　time　friction　and　tooth　backlash　were　considered　in　the　mode.　The　establishment　of　the　model　is　helpful　to　study　gear　vibration　response　under　the　condition　of　multiple　factors　and　provide　simulation　model　for　research　on　crack　propagation.