The invention discloses an American cockroach medicinal composition for curing ulcers or ulcerative inflammation. The medicinal composition is mainly prepared from an active ingredient mixture prepared by mixing an American cockroach extract and montmorillonite powder. The weight part ratio of the American cockroach extract to the montmorillonite powder is equal to 0.8-1.2:0.5-6. A preparation method of the American cockroach medicinal composition for curing the ulcers or the ulcerative inflammation comprises the following steps of: preparing the American cockroach extract, mixing active ingredients, and preparing medicaments. The medicinal composition has simple preparation method, fully exerts effects of the American cockroach extract, and has obvious effects of effectively curing diseases such as oral ulcers, recurrent aphthous ulcers, oral lichen planus, oral mucosal injury (behcet disease, herpes simplex, leukoplakia, discoid lupus erythematosus, hand-foot-and-mouth disease, scalds, chemotherapy, radiotherapy and the like) caused by various reasons, reflux esophagitis, eophageal ucers, radiation esophagitis, ulcerative colitis, radiation proctitis, and diarrhea, and hematochezia with mucosal injury, and the like.