Based on numerical simulation tools, the radial pulse laser welding process of a pressure sensor core is simulated. The model describes the equivalent heat source formed by the laser, heat transfer and phase transformation of 316L, the transient stress field formed by heat affected zone, and residual stress formed after welding. At the same time, according to the measured depth of the molten pool formed by various laser welding process parameters, calibration of the equivalent heat source model is finished, and the deviation values are within 8%. The comparative analysis between the calculated value of residual stress and measured residual stress value by X-ray diffraction method shows that the two results are consistent, and the deviation values are within 15%. It is verified that the engineering needs of study for influence law of process parameters and parameter optimization are met by the accuracy of laser welding model.