5CrNiMoLaSr modified die steel is a new type of die steel with great application prospects, and the microstructure, mechanical properties and wear resistance at room temperature and high temperature of 500 ℃ for forged 5CrNiMoLaSr modified die steel were studied, and a comparative analysis was conducted with commercial 5CrNiMo die steel. Then, the micro mechanism was briefly discussed. The results show that compared with the commercial 5CrNiMo die steel, the microstructure of forged 5CrNiMoLaSr modified die steel is finer and more uniform. At room temperature, the tensile strength is increased by 224 MPa and the yield strength is increased by 207 MPa, and the tensile strength at high temperature of 500 ℃ is increased by 314 MPa and the yield strength is increased by 285 MPa. At room temperature and high temperature of 500 ℃, the elongation is increased slightly, and the wear volumes are decreased by 1.1×10-2   and 5.3×10-2 mm3, respectively. Rare earth La and rare earth inclusions have a hindering effect on the grain boundaries, reducing the segregation of impurity elements at grain boundaries and promoting the dispersed distribution of alloy element Sr within the grains.