Abstract: Based on cold metal transfer (CMT) welding technology, welding test of 1.2 mm thick DP980 dual phase steel was carried out. Effects of wire feeding speed of 3～6 m/min and welding speed of 350～600 mm/min on the microstructure and mechanical properties of welded joints were investigated. The results showed that DP980 dual phase steel welds with no obvious defects and good formability could be prepared by CMT lap welding process. Heat affected zone of welded joints was divided into three parts, namely coarse-grained zone, fine-grained zone and incomplete softening zone, which was mainly composed of martensite, ferrite and a small amount of bainite. With the increase of wire feeding speed, grain size of coarse-grain zone increased from 13.89 μm to 25.17 μm. However, with the increase of welding speed, grain size of coarse-grain zone decreased from 26.86 μm to 16.11 μm. Average microhardness of the complete phase transition fine grain zone was up to 400 HV, while that of the softened zone was down to 260 HV. Under conditions of wire feeding speed of 3 m/min and welding speed of 500 mm/min, tensile properties of the welds were the best, and the tensile strength could reach 967 MPa. Due to the enrichment of ferrite in the softening zone, the fracture was generated in the softening zone, and the fracture mode was ductile fracture.Highlights: (1) Aiming at the difficulty in welding of automobile steel sheet, CMT process with characteristics of low heat input welding was proposed.(2) Influence of wire feeding speed and welding speed on microstructure evolution and mechanical properties of DP980 dual phase steel CMT welded joints were studied. The research results could provide theoretical basis and data support for the actual production of the factory.