The influence of welding speed on joint formation, microstructure evolution, and mechanical properties of 2 mm thick QP980 high strength steel were studied by using a laser beam with a spot diameter of 0.1 mm. It was found that with the decrease of welding speed, the cross section morphology change from nail shape to hourglass shape, and finally to straight cylinder shape. The weld melting zone is composed of coarse martensite, and the heat affected zone is mainly composed of fine martensite. The hardness is higher than that of the base metal. The hardness of the tempering zone is lower than that of the base metal due to the decomposition of martensite in the original base metal. However, with the increase of welding speed, the decomposition degree of martensite decreases gradually. Due to the hardening of the weld, the elongation after fracture of the welded joint decreases. The tensile fracture morphology at different welding speeds shows that it is ductile fracture.