Abstract: The microstructure and mechanical property of the plasma cladding 420 stainless steel coating were characterized, and the effects of the tempering temperature on the microstructure and mechanical properties of the coating were studied. The results show that with the increase of the tempering temperature, the lath martensite in the coating is gradually decomposed. The amount of carbide increases with the increase of the content of transformed austenite. When the tempering temperature increases from 450 ℃to 500 ℃, the hardness and tensile strength of the coating increase slightly due to the precipitation of dispersed M₇C₃ carbides and the strengthening of the second phase. With the further increase of tempering temperature to 650 ℃, the degree of maraging and the content of inverter austenite increase, the hard M₇C₃ carbide is coarsened and partially transformed into soft M₂₃C₆ carbide, and the hardness and tensile strength of the coating decrease significantly. The fracture mechanism of the coating changes from mixed fracture to plastic fracture with the increase of tempering temperature.The optimal tempering temperature of 420 stainless steel coating is 500 ℃.