The invention relates to an external plaster for treating prosopospasm and a preparation method. The external plaster for treating prosopospasm comprises a raw material group A of alangium lamarchii thwaites root, amber, fourstamen stephania root, periostracum cicadae, cissampelos pareira, asarum herb, zanthoxylum nitidum, spatholobus stem, safflower, centipede, herba siegesbeckiae, clematis root and long-nosed pit viper; and a raw material group B of rosin, beeswax, a hot melt adhesive, far-infrared ceramic powder, camphor, borneol, laurocapram and sesame oil. The method comprises the following steps: crushing the raw material group A into fine powder, weighting and uniformly mixing for standby, placing rosin, beeswax, the hot melt adhesive and sesame oil in an iron pan for heating to completely fuse, adding camphor and borneol and stirring for completely fusing, then adding fine powder of the raw material group A, adding far-infrared ceramic powder and laurocapram in order, uniformly stirring, and paving the paste to obtain the products. The external plaster is used on the wounded part, and is directly reached on the wounded part, the curative effect is rapid, the curative effect is obvious, and the side effect is little, and the external plaster has good application value.