Cold spray in used to form Al coating on AZ31 magnesium alloy.Several parameters, such as spraying distance, gas temperature, and gas pressure are selected as the main processing parameters for cold spray.According to orthogonal design, orthogonal experiments are designed for the optimization of processing parameters.coating density is employed to test processing result.Optimized Al coating on AZ31 magnesium alloy are sprayed by spraying distance 30 mm under pressure of 2.1 MPa at 310 C.