Current research findings generally agree that the occurrence of tumors is the result of a combination of factors, and the occurrence of oral cancer is no exception. The suspected etiological factors leading to the occurrence of oral cancer are broadly divided into intrinsic factors and extrinsic factors. Intrinsic factors include genetic susceptibility, psychosomatic factors, immune factors, hormone levels and various genetic mutations. It is important to emphasize that oral cancer, like most other tumors, is not directly inherited, but is expressed through genetic “susceptibility”, which is an individual quality that predisposes to cancer and requires the combined effect of other factors to cause cancer. However, individuals with a clear family history of cancer need to be more vigilant. Maintaining a positive, optimistic and cheerful state of mind is very helpful to prevent the occurrence of oral cancer. External factors include physical and chemical factors. It should be noted that there is a clear correlation between the occurrence of oral cancer and smoking and alcohol consumption. Tobacco contains many mutagens, which are closely related to oral cancer, while alcohol is a cancer promoter. Chewing tobacco is more harmful than smoking to cause oral cancer. In Hunan and Hainan in southern China, many people have the habit of chewing betel nut, which is an important factor leading to the high incidence of oral cancer in these areas. Long-term chronic stimulation is suspected to be a carcinogenic factor. Long-term and frequent stimulation of the oral mucosa in the corresponding parts of the patient’s mouth by the residual roots, sharp tooth tips and unsuitable dentures can produce chronic ulcers and even cancer. Long-term cigar smoke and pipe smokers are prone to lip cancer; sunlight exposure is one of the causes of skin cancer, which especially increases the risk of lip cancer. Various drugs increase the risk of tumor development, and the use of immunosuppressive drugs increases the risk of oral cancer. Studies have also confirmed that viruses, especially human papilloma virus infection, may induce oral cancer. Malnutrition, especially vitamin A and micronutrient deficiency, can cause epithelial thickening and hyperkeratosis of oral mucosa, which is also related to the occurrence of oral cancer.