Abstract: Experimental design was employed for 1.7 mm DP600 dual phase steel in order to optimize the laser welded joint mechanical property. The laser power, welding speed, focal point position and side-blowing shield gas flow were chosen as the process parameters and the mathematical model between the tensile strength of joint and the four process parameters were obtained by using regression analysis. The interaction effects of the welding speed and side-blowing shield gas on welding quality were explored. The optimal combination of welding process parameters was achieved using genetic algorithm and the largest tensile strength of welding joint was obtained as the welding power was 1.7 kW, welding speed was 25 mm/s, side-blowing shield gas flow was 2.4 m3/h, focal point position was -1 mm. The results of validation experiments showed that the model generally had a good effect and high precision, and its average relative error was within 5%, this study can effectively forecast and optimize the laser welding quality for the dual phase steel with the thickness of 1.7 mm.