Abstract: A thermal elastic-plastic finite element model is established to simulate the three-point welding of compressor shell and cylinder.Several sensitivity parameters are discussed such as the height of the compressor shell,the material properties of the cylinder and the wall thickness in specific locations of the cylinder.The width change becomes smaller when the cast steel is used for the cylinder material,and the contact condition between the cylinder and the shell has significant effects on the deformation of the cylinder.In order to improve the efficiency of calculating and maintain the accuracy of the results,an inherent strain FE model based on the thermal elastic-plastic finite element model is developed.The result obtained by using the inherent strain method agrees well with both the thermal elastic-plastic result and the experimental result.Moreover,the inherent strain method can greatly reduce the computing time.This method can be applied in optimization of large and complex welded structures.