Abstract: In this paper, the welding thermal simulation was performed on the forged high-Mn twinning induced plasticity steel by setting different peak temperatures (850, 950, 1050, 1 150 and 1 250 ℃) in each interval of the heat affected zone of the welded joint using the Gleeble 3500 thermal simulation tester. Electron backscatter diffraction system, scanning electron microscopy and X-ray diffraction were used to analyze the changes in the microstructure and properties of the forged base material after the thermal action of welding. The results show that the microstructure of twinning induced plasticity (TWIP) steel before and after the thermal action is all-austenitic with equiaxed grains, and the grain size firstly decreases and then increases with the rise of the peak temperature, but is still lower than that of the base material. The tensile properties in the heat-affected zone are better than those of the base material, mainly due to the occurrence of fine grain strengthening. The impact toughness of the twin-induced plasticity steel is related with grain size in this study, and the finer the grain size, the worse the impact toughness. AlN particles were found at the bottom of the dimple of the impact fracture.