NOVELTY - The two brake friction surface of the brake disc of a wind power generating unit is cleaned and blasted. The brake disc and two tower cylinder flange contact by a cold laminating film, and then the two tower cylinder flange contact surfaces are sprayed with zinc. Using acetylene-oxygen continuously, a honeycomb-shaped zinc spraying layer is formed with a thickness of 100-140 mu m and a zinc content of not less than 99.995%. An outer composite coating is then provided to the brake disc and wall except the other surface of cold laminating film.    USE - Composite coating of braking disc of wind power generating units.    ADVANTAGE - The method improves the service life, corrosion resistance, and age resistance of braking discs of wind power generating units. The composite coating has excellent elasticity, wear resistance, weather resistance, and adhesive force.    DETAILED DESCRIPTION - The two brake friction surface of the brake disc of a wind power generating unit is cleaned using an acid or alkaline detergent, to remove oil impurities from the substrate surface. The braking friction surface is blasted to clear the surface of base material, rust, and other impurities. The roughness of the standard sample is set to 40-70 mu m. The brake disc and two tower cylinder flange contact by a cold laminating film for covering protection, and then the two tower cylinder flange contact surfaces are sprayed with zinc. Using acetylene-oxygen continuously, a honeycomb-shaped zinc spraying layer is formed with a thickness of 100-140 mu m and a zinc content of not less than 99.995%. An outer composite coating is then provided to the brake disc and wall except the other surface of cold laminating film by spraying an epoxy zinc-enriched primer and curing agent in a volume ratio of 4:1 at 10-20 degrees C using a spray gun to form a primer of thickness 45-55 mu m, drying the primer for 6-8 hours, spraying a middle paint containing polyamide epoxy paint and firming agent in a volume ratio of 3:1 to by a spray gun to a thickness of 130-140 mu m, drying of 8-12 hours, and spraying paint containing polyurethane and curing agent in a volume ratio of 7:1 by a spray gun to a thickness of 50-60 mu m, and drying for 7-10 days.