Abstract: A new austenitic hot die steel was produced by decreasing Cr,Mo contents and increasing Si,Mn contents to compare with foreign GP steel.The mechanical properties,microstructure and the thermostability at 750 ℃ of the two steels were investigated after treated at the same smelting,forging and heat treatment conditions.The results indicate that they had similar vertical impact toughness,while the horizontal impact toughness of testing steels was superior to GP steel,that testing steel had better isotropic property.Its tensile strenghth and ductility property of testing steel were better than that of GP steel.Both the hardnesses kept stable at 750 ℃ for 20 h,and the hardness of testing steel was about 2 HRC higher than that of GP steel during thermostability test.