Abstract: The brittlement and softening of HAZ of high strength steel JFE980S were studied by thermal simulation test.After the thermal cycle curve of laser hybrid welding and MAG welding being measured,the HAZ of two welding methods were simulated by means of the thermal simulation machine of Gleeble3500,and the microstructure,tensile strength and the impact toughness at-20℃ of the specimens were tested and analyzed.The results indicate that the residence time of peak-temperature,t_8/5 and t_5/3 in laser-arc hybrid welding are all less than those in MAG welding.The impact toughness of the coarse grained region in joint by hybrid welding is as two times high as that by MAG welding.The tensile strength of the incomplete phase transformation region was increased by more than 100 MPa,which was compared with the common MAG welding.