Provided is cataplasma for treating body surface infectious diseases applied to the technical field of medicines. The product prescription comprises cortex phellodendri chinensis, calcined gypsum, sodium polyacrylate, peach gum, polyvinylpyrrolidone, sodium carboxymethylcellulose, kaolin, glycerol, dihydroxyaluminium aminoacetate, tartaric acid, azone, diethylamine tetraacetic acid disodium and water. The preparation method includes solving the polyvinylpyrrolidone in water completely, adding the sodium carboxymethylcellulose and the peach gum into the mixture, mixing the mixture evenly, continuously adding the tartaric acid to obtain mixing liquid 1, namely water phase, placing the sodium polyacrylate, the diethylamine tetraacetic acid disodium, the dihydroxyaluminium aminoacetate, the azone and the kaolin in the glycerin, stirring the mixture to enable the mixture to be completely swelled, then adding the cortex phellodendri chinensis and the calcined gypsum, evenly stirring the mixture to obtain mixing liquid, namely oil phase 2, adding the water phase into the oil phase, completely stirring the mixture till the mixture is even, coating paste on medical non-woven fabric through a compression molding method, conducting film bonding and slice cutting, and placing the mixture to conduct complete crosslinking to obtain the cataplasma. The cataplasma is simple in using method, suitable for being applied in summer, free of side effects, good in air permeability, free of pollution to clothes and free of residual. Users do not have uncomfortable feeling if using the cataplasma, and the cataplasma has no stimulation and anaphylaxis on skins.