Ordinary mouth ulcers usually heal within 1-14 days, and cancer is not considered in this case. However, if it does not heal for more than 2 months, the possibility of cancerous ulcers should be considered. Mouth ulcers are the more common oral diseases. There are many reasons for mouth ulcers not healing, such as local irritation, poor nutrition, vitamin deficiency, micronutrient deficiency, overexertion, oral infection, endocrine disorder, etc. However, if the oral ulcer does not heal for a long time and there is a lump, pain or foul-smelling secretion in the area, the possibility of cancer should be considered, and it is recommended to visit the stomatology or oncology department of the hospital for a clear diagnosis in time. It is recommended that patients should pay attention to oral hygiene, gargle with light salt water, eat a nutritious diet, avoid stimulating food, don’t stay up late and ensure sufficient sleep.