Abstract: Al-Si coated hot forming steel was welded by fiber laser wire filling welding, and the effect of laser power on the macroscopic morphology and microstructure of the welded joint was studied.The results show that in the process of laser wire filling welding, the welding wire is fused into the molten pool stably in the form of liquid bridge transition, and the weld is well formed. After heat treatment, the weld microstructure is mainly martensite and δ-ferrite. With the increase of laser power, the content of Al in weld first increases and then decreases, which make the ratio of δ-ferrite in weld first increase and then decrease, the tensile strength of the welded joint first decreases and then increases.When the laser power is 3.5 kW, the tensile strength of the welded joint reaches 1490 MPa and the strength coefficient of the welded joint is about 97.6%.