1.6 mm DP590 and 2.0 mm DP780 were welded by laser tailor welding under different welding speeds and different laser power, the macro-morphology, microstructure, tensile properties, hole expanding rate and cupping value of the welded joints were tested, analyzed the influence of welding speed on microstructure and tensile properties, revealed the forming performance of welding joints. The result indicate that, the laser welding joints were well formed, the microstructure of weld zone was columnar martensite, the microstructure in the heat-affected zone were composed of martensite and ferrite, and the morphology of microstructure between weld zone and heat-affected zone were slightly different; the welding speed had no obvious effect on the microstructure, yield strength and tensile strength of the joints, increased the welding speed gradually, the elongation of welded joints showed an upward trend; the cupping value and hole expanding rate of laser welded plate were lower than that of two side base metal, but the base material of both sides were vulnerable spot in the forming process. When the laser power was 3.72 kW, the welding speed was 5.5 m/min, the joints shower the best tensile properties and forming performance.