Abstract: It is an optimum method to solve the problem on the appearance quality and tightness of stainless steel car body by replacing resistance spot welding with lap laser welding.But in the experiments of partial penetration lap laser welding,the shape of molten pool was found to be similar with a vase in the common processing parameters,which was different from the normal laser conductive welding or the laser deep penetration welding.By using the software of ABAQUS,the welding temperature fields were simulated with different heat source models,such as Gauss heat source,Gauss heat source+conical heat source,and 3-D conical heat source+inverted conical heat source+ellipsoid heat source.The results indicate that the shapes of molten pool simulated by using 3-D conical heat source+inverted conical heat source+ellipsoid heat source agree well with the experimental results.