Aiming at the laser welding of overlap joints of 3 mm+2.5 mm weathering steel material,the influence of welding parameters on weld penetration and weld width was studied by surfacing welding test,and the relationship between weld penetration and weld width with shear force was studied. The metallographic structure,hardness and tensile test results of the joint were analyzed. The results show that the optimum process parameters are obtained,and the shear force reaches a stable value when the weld penetration is greater than 1 mm when fixed weld width in the range of 0.7 ～0.9 mm. When the weld penetration is greater than 1 mm,the maximum shear force is 26 kN with a uniformly mechanical properties of the whole joint and a stability laser welding process. The hardness of weld and heat affected zone is higher than that of base metal,and there is a certain tendency of hardening.