Laser cladding technology was used to prepare WC/Ni cladding layer on the surface of cold work die steel (Cr12MoV), and the changes of its composition and red hardness were studied. The microhardness tester and ring block friction and wear testing machine were used to test the red hardness and wear resistance of the cladding layer. The results show that when the laser power is 1.0 kW, the powder feeding voltage is 8 V, and the scanning speed is 2 mm/s, the cladding layer is mainly composed of cladding layer mainly composed of γ-Ni (Fe), W2C, Cr7C3, Fe6C2, Fe6W6C, WC, Fe2B, etc. phase and M23C6 eutectic compound composition; when the red hardness test temperature is 200 ℃, the hardness of the cladding layer can reach 57 HRC or more, higher than the substrate 52.1 HRC, when the temperature reaches 400 ℃, the hardness of the cladding layer still reaches 47 HRC or more, and the substrate only has 33.1 HRC; the weight loss of the cladding layer reaches a maximum of 1.7 mg at a red hardness test temperature of 400 ℃ but is still less than the weight loss of the substrate at ordinaryl temperature of 1.9 mg; the red hardness test within 500 ℃ only affects the microstructure of the cladding layer; the degree of chemical conversion has no great influence on the strengthening mechanism and composition of the cladding layer; the cladding layer belongs to the abrasive mechanism within 300 ℃, and evolves into adhesive wear when the temperature reaches above 400 ℃.