Abstract: DP590 steel has been widely applied in the field of automobile industry.In present paper, the double-pass welding process in single-sided of CO₂ gas shielding was simulated by using parametric programming language and life-and-death cell technology.The numerical simulation results were compared with the experimental results obtained with the same preconditions.The results showed that the simulation result of temperature distribution within the sample is generally consistent with the measured temperature value.Compared with that of the first welding pass, the thermal cycling of the second pass has a greater impact on microstructure across the heat-affected zone.Because of the great influence of reheating temperature on the multi-pass welding process, it will be more advisable to maintain the temperature of the steel at around 200℃ at the beginning of second welding pass.