The invention discloses a wallboard for boxcars, which is a laminar composite material. A metal ceramic composite coating is sprayed on the external surface of an aluminum honeycomb substrate, and a high-polymer coating is arranged on the external surface of the metal ceramic composite coating. Iron powder and ZrO2 powder in the metal ceramic composite powder generate an amorphous phase, thereby enhancing the bonding property with the aluminum cellular board, and enhancing the strength and hardness of the coating. The high-polymer coating is arranged on the external surface of the metal ceramic composite coating by dipping or brushing; and the anticorrosive component and sun protection component contained in the high-polymer coating enhance the corrosion resistance of the coating under the synergistic actions of other components. The added hypophosphorous acid aluminum powder is wrapped as an inorganic phase by various components in the high-polymer paint, thereby performing the synergistic function. The sun protection component is added into the high-polymer coating in a composite wrapping mode to perform the synergistic function. The wallboard can avoid peeling, and has longer service life.