The paper adopts the fiber coupled diode laser welding system of LDF4000-40 and studies the welding performances of galvanized sheet with different thicknesses (t=0.7/1.4 mm) in the automobile industry. The results show that compared with the CO2 laser welding, it has better process stability, better welding bead with easier control, and faster welding speed. The tensile strength and elongation of the galvanized sheet welded joints meet the standard requirements of the motor industry and the cracks generate in the base metal parts. The galvanized steel weld metal includes ferrite and pearlite, so that the weld metal is 1.5 times the hardness of the base metal. Under the same condition of laser output power, the welding speed of fiber coupled diode laser increased more than 1.2 times compared with that of the CO2 laser.