Abstract: It was extremely rare of oral mucosal lesions caused by Escherichia coli. A patient with oral mucosa ulcer was reported. Tissue collected from oral mucosa ulcer was cultured and antibiotics sensitivity was tested. It was demonstrated that the ulcerative stomatitis was caused by escherichia coli infection, and the bacterial was sensitive to Imipenem-Cilastation Sodium. After antibiotics treatment, the oral mucosa ulcer got significant remission.