Abstract: The effect of post weld heat treatment on the microstructure and properties of laser welded joint of DP980 steel was studied by means of SEM observation, hardness test and tensile test.The results show that the proportion of martensite phase in each region of the DP980 steel laser welded joint is significantly different.Compared with that of the base metal, the proportion of martensite in the fusion zone is higher, while the proportion of martensite in the heat-affected zone is significantly decreased, resulted in an obvious soft zone and reducing the mechanical properties of the joint.The post weld heat treatment can improve the structure uniformity of each area of the joint, effectively eliminate the soft zone, thus improving the hardness and strength of the joint, but it reduces the plastic toughness of the joint.