The possible causes of post-surgical oral ulcers include psychosomatic factors, changes in the intraoral environment, and antibiotic application, as follows. 1. Psychological factors: Surgery and disease may lead to tension, anxiety, depression and other emotions, which have a certain relationship with the occurrence of mouth ulcers. 2. Change of oral environment: surgery may affect the normal secretion of saliva by salivary glands, leading to the destruction of oral self-cleaning function, micro-ecological disorders and oral ulcers. 3. Antibiotic application: Antibiotics are usually applied during and after surgery to prevent infection, which may lead to dysfunction of intraoral flora and cause oral ulcers. To avoid this problem, the use of antibiotics must be in strict accordance with the doctor’s instructions and should not be abused. There may be other causes of post-surgical mouth ulcers, and it is recommended to visit the hospital for early professional treatment.