A continuous fiber laser is used for the tailored blank laser welding of 800 MPa and 1000 MPa dual-phase (DP) steels and the effects of martensite content on the microstructure and properties of laser welded DP steel joints are investigated. The results show that the laser welded DP steel joints with different martensite contents are all composed of the full-martensite area and the non-full-phase-transformation area. The widths and microhardness of two laser welded joints are relatively reduced, and their tensile fracture positions are both in the base materials (BMs). The 1000 MPa welded DP steel joint directly cracks and expands along the non-full transformation area during the erichson test and its erichson value is 85.0% that of the BM. In contrast, the 800 MPa welded DP steel joint cracks perpendicular to the full-martensite area and its erichson value is up to 91.7% that of the BM.