Die casting mold is an important process equipment used in production process of die-casting, which has an important impact on quality of casting. Quality of die casting mold affects strength and surface quality of casting. Since liquid alloy enters cavity at a high temperature and high speed, it causes impact on mold parts, and die casting mold has higher requirements on wear resistance, corrosion resistance, strength and so on. Excellent molds can not only reduce frequency of replacement, reduce production costs, improve production efficiency, but also help to form excellent castings. Therefore, how to improve quality of die casting mold and extend their service life is an important issue to be solved in actual production and research. HHD steel is a new type of hot work die steel with high hardenability. It has good hardenability and can obtain a toughened structure of 10 ~ 20nm carbides with a layered structure between low-carbon lath martensite crystals and a dense oxide film resistant to high temperature oxidation. Soft nitriding process is widely used for improving wear resistance and corrosion resistance of die casting mold parts, and is used for surface treatment of mechanical structural parts or mold parts. Soft nitridation is process of infiltrating carbon and nitrogen atoms on the surface of materials through various chemical or physical means. Hardness and fatigue strength of surface nitrided layer structure after soft nitridation treatment are excellent, but research on soft nitridation system of die casting mold parts is still less. Effect of soft nitriding treatment temperature on properties of die-casting HHD steel is mainly studied.