Abstract: The Co40 alloy surfacing layer, Cr3C2/Co composite surfacing layers with 30wt.％ micron and nano Cr3C2 respectively on the surface of low-carbon steel were obtained by plasma surfacing. Effects of micron-Cr3C2 and nano-Cr3C2 on the microstructure and properties of the Co40 alloy surfacing layer were studied comparatively. Results show that the Co40 alloy surfacing layer was composed of developed columnar crystals and reticular eutectic structure between the dendrites. The dendrites of micron-Cr3C2/Co composite surfacing layer were broken and fragmented, the growth directionality of the columnar crystals was obviously weaken and the microstructure was refined and homogenized. The crystallization way of nano-Cr3C2/Co composite surfacing layer transformed into eutectic way from hypoeutectic way, the microstructure was mainly composed of eutectic structure, which was further refined and became more homogeneous. Compared with the Co40 alloy surfacing layer, the hardness and wear resistance of the micron-Cr3C2/Co composite surfacing layer were increased by 37％ and 29％, while the hardness and wear resistance of the nano-Cr3C2/Co surfacing layer were increased by 50％ and 55％.