Die-casting is mainly made of SDK61 steel if heat treatment and nitriding surface reasonably can extend the working life over 100,000 cast to still ensure accuracy of product. Die-casting after mechanical processing for precise shape and size , then quenching at 1030°C and tempered at 560°C, received hardness 44 to 49 HRC, then nitriding at 510°C to 530°C during 6h, the surface hardness is over 900 HV ( 67HRC). With these treatments mode, die-casting has rigid enough to not sunk under high pressure, not break under changed load, not rapidly wear while working.