Oral cancer is one of the more common malignant tumors of the head and neck, and its occurrence is related to many internal and external factors, including smoking, alcohol consumption, viral infection, poor nutrition, dietary habits and local irritation, etc., among which smoking and alcohol consumption are the most dangerous. Although great progress has been made in the treatment of oral cancer by surgery, radiotherapy, chemotherapy and biological therapy, the 5-year survival rate of oral cancer still hovers around 64%, and the prognosis of patients with advanced stage is even worse. Therefore, in order to improve the survival rate and quality of oral cancer patients, we must unswervingly implement the health policy of “prevention-oriented” and strive to achieve early detection, early diagnosis and early treatment. The main risk factors of oral cancer are tobacco, heavy alcohol consumption and poor diet (including betel nut chewing), which are related to more than 90% of patients. In areas with high incidence of oral cancer, carrying out various propaganda, changing dietary structure and habits, quitting smoking, controlling the amount of alcohol consumption, regularly examining high-risk groups and closely following up patients with precancerous lesions are the most effective primary prevention measures. However, the implementation of primary prevention must be carried out after a lot of practice and long-term follow-up such as on-site research and observation, case-control studies, animal experiments and prospective studies, accumulating a lot of epidemiological and etiological data and formulating prevention programs. 2.Secondary prevention of oral cancer Secondary prevention, also known as preclinical prevention, aims at screening oral cancer and potential malignant lesions and preventing the development of primary diseases. The occurrence and development of oral cancer is a gradual evolutionary process, which can last from several years to several decades. It is generally believed that this evolutionary process goes through the following stages: hyperplasia, atypical hyperplasia, carcinoma in situ, early infiltration, and invasive carcinoma. Therefore, regular screening of high-risk groups, early detection of precancerous lesions and early cancer, timely diagnosis and treatment will effectively prevent the occurrence of oral cancer and reduce mortality. At present, the pre-cancerous lesions or states of oral cavity include oral leukoplakia, erythema, lichen planus, oral submucosa fibrosis, chronic actinic labyrinthitis and oral mucosal ulcer, etc. 3.Tertiary prevention of oral cancer Tertiary prevention, i.e. clinical (stage) prevention or rehabilitative prevention, aims at preventing recurrence or new primary cancer and minimizing mortality. If a patient with oral cancer has cancer lesions in the oral cavity months or years after receiving oral cancer treatment, it is necessary to identify whether the new lesions are recurrence due to incomplete excision of the primary lesions or the second primary cancer from the cancerous mucosa. Field cancerization refers to the genetic susceptibility of a patient, combined with the lifelong accumulation of known or unknown potential carcinogens, which increases the risk of cancer in the corresponding anatomical area and makes the patient highly susceptible to cancer. Secondary primary cancers can occur simultaneously with the primary cancer (concurrent cancers) or later (diachronic cancers). Another view is that a clone of genetically damaged precancerous cells can migrate and form a second primary cancer at another anatomical site. Apparently, in patients with oral cancer, the entire upper gastrointestinal-respiratory tract is a susceptible area. Therefore, it is not surprising that patients treated for oral cancer are at a higher risk of developing cancer again, with the incidence of second primary cancer reaching 20% within 5 years, especially when smoking, alcohol consumption and dietary risk factors persist. To prevent second primary cancers, all of the above primary prevention measures need to be intensified, including supplementation with antioxidants such as vitamin A or retinoids. Chemoprevention is the application of natural or synthetic chemicals to reverse, inhibit or stop the cancer process and prevent the development of invasive cancer. A large number of studies have been conducted on chemoprevention of oral precancerous lesions, but the reported results are mixed and still in the research stage, which cannot yet be applied on a large scale. Drugs or preparations that have been tried include vitamin A and retinoids, beta-carotene, vitamin E and selenium, COX-2 inhibitors (ketorolac gargle), adenovirus gargle, sulindac, curcumin (Curcurnin), etc.