Abstract: A mathematical model of the relationship between spraying parameters (spraying distance, spraying spacing and spraying angle) and coating thickness deviation was established based on the method of quadratic regression universal rotary composite design. The influences of spraying parameters and their interaction on the coating thickness deviation were studied. The spraying parameters of complex steel joints were optimized by using the 3D response surface model. The complex steel joints were sprayed by robot with the optimized spraying parameters, and the thickness deviation of the obtained coating was controlled within 4.51 μm. So the spraying uniformity was good.