Laser welding of the 22MnB5 steels coated with different Al-Si coating weight was conducted. The influence of the coating weight on the microstructure and mechanical performance of the welded joints was studied. The microstructure in the fusion zone of the AlSi75 and AlSi40 joints was ferrite mixed with lath martensite, while near the fusion line, abundant long strip shape ferrite was observed. The average Al content of ferrite was 5.81% and 2.82%, respectively, which was much higher than that in the fusion zone. There were apparent softening areas in the fusion zone. For the AlSi75 joint, the tensile strength was 1368.0 MPa and the total elongation was 1.6%, which were slightly lower than that of the AlSi40 joint. When the coating weight was reduced to 25 g/m2, the microstructure throughout the entire joint was only lath martensite. Meantime, the Al segregation and hardness softening were eliminated. The tensile strength was enhanced to 1571.5 MPa, and the total elongation was raised to 7.0%. The fracture mode changed from ductile fracture mixed with brittle fracture to complete ductile fracture.