The occurrence of oral cancer is related to smoking, alcohol consumption, betel nut chewing, viral infection, poor nutrition, dietary habits and local stimulation, among which smoking, alcohol consumption and betel nut chewing are the most dangerous. In some areas of Hunan and Taiwan, there is the bad habit of chewing betel nut for a long time, and research shows that the high incidence of oral cancer in these areas has a great relationship with betel nut chewing, and betel nut chewing and smoking have a synergistic effect to increase the chance of oral cancer. Therefore, smoking, alcohol and betel nut chewing should be avoided, especially for those with precancerous oral cavity lesions. In addition, we should avoid prolonged sunlight exposure to reduce the incidence of lip cancer and facial skin cancer. Poor oral hygiene or sharp irritating injuries such as root remnants, crown remnants and poor restorations in the oral cavity often form traumatic ulcers on the tongue edge or buccal mucosa, or chronic inflammatory ulcers. Long-term untreated chronic ulcers can become cancerous, especially tongue cancer is the most common. The survey found that more than half of oral cancer patients have poor oral hygiene and nearly 1/5 cases have mechanical damage factors in the oral cavity. Patients with ulcers caused by poor restorations have a 2.3 times increased risk of oral cancer. Patients who do not adhere to daily tooth brushing have 2.1 times more risk of tongue cancer and 2.4 times more risk of tumors in other parts of the mouth. Therefore, oral health checkups should be conducted regularly, and those who have prostheses such as dentures need to seek regular dental professionals and have regular oral cleaning to correct unsuitable dentures and remove bad prostheses, root and crown remnants.