The basic structure of spot welding workstation system and the special simulation software Motosim EG for YASKAWA MOTOMAN series industrial robots are introduced. The software is used for robot selection,model import and tool setting to build a complete simulation environment of MS165 spot welding robot workstation,which includes confirming robot selection and system layout,verifying robot action range,checking tooling interference,verifying action flow rhythm,writing an offline programming and so on. And it is applied in actual production. The results show that using MotoSim EG simulation software to program is more efficient and safe than field operation,and the use of offline programming calibration device can significantly improve the accuracy of offline programming and achieve the desired effect.