Abstract: Based on Box-Behnken second-order response surface methodology, the regression analysis experiments with three factors and three levels were designed. Cr2O3 coating was deposited on TC4 titanium alloy substrate by atmospheric plasma spraying(APS) technology under different process conditions and micro-hardness values were measured as the response values. The mathematical model was established between the influence factors such as spraying current, plasma gas flow and spray distance and the response values of micro-hardness. The significance of single factor and interaction effects were also discussed. The response surfaces and contour curves about the micro-hardness of the coating were obtained for process optimization and performance prediction of Cr2O3 coating sprayed by APS. The results show that the optimized second-order model was HV0.3=17 330.35+10.15I-735.74QAr-47.57d + 0.073I·d-0.014I2+7.8QAr2. The maximum micro-hardness of 1 271.72 HV0.3 could be obtained with the prediction parameters of the current of 588.47 A, flow of argon of 40.00 L·min-1 and spray distance of 80.00 mm. The precipitated maximum micro-hardness agreed with the factually measured maximum hardness of 1 284.7 HV0.3.