The invention relate to a chemical plating nickel phosphor alloy coating manufacturing method. It includes oil removing, rust removing, activating, chemical plating, and post treatment. Its bath uses secondary phosphorous acid as reducer, nickel sulfate as main salt, adds complexing agent, buffering agent, stabilizing agent, etc. It optimizes bath constituent and chemical plating technological parameter by homogeneous design and single factor test method to form active surface, reduce nickel phosphor alloy coating at certain chemical plating condition. The invention has the advantages of safe, reliable, even coating, long useful life, cathodic protection function for copper alloy screw propeller, lowering marine life defilement.