When there are pain, spots, numbness, lumps, ulcers, sores, loose teeth and other discomforts in the mouth, one needs to be alert to oral cancer. 1. Pain: the most common clinical symptom of oral cancer is acute inflammation secondary to tumor enlargement; pain can be induced when eating sweet and sour, spicy and stimulating food, or talking, drinking, eating and other actions. 2. Spots: more often manifested as white spots, less often manifested as erythema, but the malignancy of erythema is very high. 3. Numbness: if the tumor is located in the maxilla, it may compress the maxillary sinus, or if the occlusion is located in the mandible, it may invade the mandibular neural tube, and numbness of the lower lip may appear. 4. Lump: lump is a common complaint symptom of oral cancer patients, mostly infiltrating and destroying the surrounding tissues, and pain, ulceration and metastasis may occur in the later stage; 5. Ulcers and ulcers: localized ulcers and ulcers with increasing area, hard base, unclear boundaries and long duration, such as deep and large ulcers for more than one month without healing tendency. 6. Loose teeth: when oral cancer invades bone tissues in the process of development, it can cause gradual resorption and destruction of the alveolar grooves, making teeth loose or even fall off. In addition, the tumor in the oral cavity may feel as if there is something in the mouth, and the language is not clear; tongue or base of tongue cancer may invade the hypoglossal nerve and paralyze the tongue muscle. When the above symptoms appear, one should consult the doctor in time and give targeted treatment after the doctor clarifies the cause of the disease.