Objective To prepare coating with high hardness, this paper studied the main factors influencing the hardness of Cr₂O₃ coating. Methods The influences of spraying distance and air pressure on the coating microstructure were studied by single variable method, and then the effects of three factors including spraying current, air pressure and spray distance on the hardness of Cr₂O₃ coating were investigated with orthogonal experiments. Results The results showed that the primary and secondary order of the Cr₂O₃ coating hardness by technical parameters was: air pressure, spray current, and then spraying distance. Conclusion The optimal combination of process parameters for high hardness coating was: air pressure 0. 4 MPa, spraying current 270 A, spraying distance 200 mm. The coating was dense, uniform and with low porosity.