Abstract: The effects of two phase heat treatment with different temperature and time on the microstructure and mechanical properties of DP780 dual phase steel were studied by OM and tensile testing machine. The results show that the microstructure of cold rolled DP780 dual phase steel is martensite and ferrite after being austenitized at 870 ℃ for 60 min and then heat treated at 780 ℃ for different time. With the increase of holding time, the martensite content in the test steel decreases gradually. The elongation of the steel after heat treatment at 780 ℃×5 min reaches the maximum value of 18%, and the tensile strength is close to 1100 MPa, and the matching of strength and plastic properties of the test steel is best.