In this paper,the hardfacing technology of nickel based cemented carbide layer prepared by plasma powder spray welding on a 20CrNiMo product is studied,and the PT,microstructure,hardness and SEM scan are analyzed. The experimental results show that the preparation procedure of cemented carbide layer has good repeatability,smooth bond line and no defects. There is a precipitate reducing band about 100 μm away from the bond line,a 2.5 μm wide white bright band at the bond line, and a about 100～200 μm wide diffusion band at the side of the base metal of the bond line. The microstructure of the diffusion band is a mixture of pearlitic ferrite and WC. Through SEM-EDS analysis,the microstructure of the welding layer is composed of γ-Ni solid solution matrix and interdendritic carbide eutectic structure. The hardness testing of the hardfacing layer is evenly distributed,and the hardness meets the requirements. At the same time,the welding layer has the characteristics of work hardening.