The welding test of DP500 dual-phase steel sheet of 0.65 mm is implemented by the Nd:YAG solid pulsed laser welder. The pulsed laser weld surface and cross-section morphology are analyzed, and the paper focuses on the weld solidification characteristics under different pulse laser frequencies and the relationship between microstructure grain and microhardness. The result shows that each of the welding spots forming the weld seam can be divided into two parts: welding spot overlap region and unoverlap region. With the change of the pulse laser frequency, the morphology of weld and the welding spot overlapping ratio both change, and the microstructure grain exhibits heterogeneity. Meanwhile, microhardness distribution appears to be fluctuant, the minimum microhardness value appears in the welding spot overlap region while, the maximum microhardness value appears in the unoverlap region. With the pulse laser frequency increasing, the difference of microstructure grain decreases and the fluctuation of the microhardness distribution along the longitudinal section of the weld center is also gradually reduced.