The work aims to improve the comprehensive mechanical properties and hygrothermal properties of composite materials by using the optimum thickness ratio of environmental coating system for composite materials. For composite primer/topcoat system, thickness control of coating was transformed to layer control by controlling the spraying process and 4 groups of primer/topcoat in different layers were designed. Flexibility, adhesion, impact resistance and hygrothermal properties of anticorrosion coating system were used to systematically characterize he single-layer and multi-layer composite materials. As the coating thickness increased, flexibility, adhesion and impact resistance of coating system decreased; the coating could effectively reduce the heat absorption rate and provided better heat and humidity resistance by isolating the direct contact between water and composite materials, and as the coating thickness increased, the heat and humidity resistance increased. The relation between flexibility, adhesion, impact resistance and environmental resistance of coating system and the coating thickness was not just linear. A test scheme on thickness optimization of organic coating is put forward by controlling the thickness of single-layer coating to transform the thickness optimization into the layer optimization and better mechanical properties and hygrothermal properties of coating under the design of (1′2) thickness are determined.