Based on the relationship between the material′s thermophysical parameters and temperature change, a 3D transient model of waterguided laser for removing paint on the surface of stainless steel matrix was established with Ansys, and the distribution of temperature field was obtained through numerical simulation during the simulation process. The influence of peak laser power, pulse width and processing speed on the distribution of simulated temperature field is found through single-factor simulation test. The simulation results show that the maximum temperature is concentrated in the center of heat source, and increases with the increase of laser peak power and pulse width, and decreases with the increase of processing speed. According to the maximum working temperature of 316 L stainless steel substrate and the melting temperature of fluorocarbon paint layer combined with the distribution of simulated temperature field, the optimum technological parameters were determined. The simulation predicted value was close to the test result, which proved the feasibility of the finite element simulation of water-guided laser on the surface of stainless steel substrate for paint removal.