Abstract: The process parameters of high-velocity oxy-fuel(HVOF) spraying CuNiIn coating were optimized to prepare CuNiIn coating with excellent properties on the surface of TC21 titanium alloy. The effects of oxygen flow rate, kerosene flow rate, powder feeding speed and spraying distance on spraying temperature, microhardness, spraying residual stress and bonding strength of the coating were systematically and comprehensively studied by the orthogonal test with four factors and three levels, and the optimal process parameters based on spray temperature, spray residual stress and coating bonding strength were obtained. The contaminants at the coating interface and the properties of resistance to fretting wear of Cu Ni In coating were also tested and investigated. The results show that these key parameters have influences on the deposition quality and the stress state of the coating through changing the spraying temperature and speed, so as to further influence the performance of sprayed coating. It concludes that kerosene flow is the major factor that influences the temperature of deposited coating;powder feeding speed is the major factor that influences the residual stress of deposited coating; oxygen flow, powder feeding speed and spraying distance are all the major factors that influence the bonding strength of deposited coating. The contaminants at the coating interface mainly come from the residue formed when the sand is broken into the matrix during the sand blowing process, which has no direct relationship with the spraying process. Under the same test conditions, the fretting wear rate of TC21 sample coated with CuNiIn coating is only one thousandth of that without coating. The CuNiIn coating prepared by the parameter optimization(oxygen flow:1850 SCFH; kerosene flow:6.0 GPH; powder feeding speed:4.5 r/min; spraying distance:330 mm) shows excellent performance: the microstr-ucture of the coating is dense with less voids, the coating interface is almost pollution-free, and the coating shows good combination with the matrix and excellent anti-fretting wear properties.