Abstract: The surface of TC21 titanium alloy was treated by pretreatment of grit blasting and shot peening and high velocity oxy-fuel spraying WC-17Co. The effects of grit blasting and shot peening pretreatment on TC21 titanium alloy by supersonic flame spraying WC-17Co coating were studied. The results show that the microstructure of WC-17Co coating with grit blasting and shot peening pretreatment is uniform and well combined with the substrate. The protrusion or sag of the bonding surface between the coating and the substrate is sharper after grit blasting, and there is the embedding of foreign alumina sand particles, while the bonding surface after shot peening pretreatment is convex and concave, without introducing foreign impurities. The effect of grit blasting on the surface roughness of TC21 titanium alloy is more significant than that of shot peening pretreatment, but the surface roughness of WC-17Co coating is not significantly different with grit blasting and shot peening pretreatment, and the surface roughness of WC-17Co coating can reach 4.602 μm. The hardness of WC-17Co coating with grit blasting and shot peening pretreatment is similar, and the hardness is 1600-1800 HK0.98, which is more than4 times higher than the hardness of matrix. The porosity of the coating with grit blasting and shot peening pretreatment is not different, but near the interface between coating and substrate, the porosity of WC-17Co coating with grit blasting pretreatment is higher than that with shot peening pretreatment.