Abstract: In order to analyze the effect of laser welding heat input on explosion-proof force of car battery covers, finite element method (FEM) was used to simulate the temperature field of explosion-proof valves during laser welding. According to the effect of recrystallization annealing and homogenization annealing on crystal segregation of Al3003 and microstructures of explosion zone, the variation law of explosion-proof force was analyzed at different welding heat inputs. Meanwhile, the laser welding process parameters were optimized according to the explosion-proof force target range of 0.9 ± 0.05 MPa. It is showed that the explosion-proof force presents a parabola trend with the increase of laser powers. Explosion-proof force is closer to the target value of 0.9 MPa when the laser welding process parameters are laser power of 1 050 W, z-value of + 161 mm, and welding speed of 50 mm/s.