Not long ago, a 26-year-old man had occasional spontaneous bleeding from his gums for more than 1 month. Because he was busy at work, he took a weekend holiday to visit a local hospital for dental cleaning treatment. On the day after the cleaning, there was extensive bleeding from the gums of the whole mouth, and at midnight of the same day, he went to the emergency department of the hospital dentistry to stop the bleeding. The doctor used hemostatic drug cotton tablets such as pay renin and Mang’s solution, and pressure to stop the bleeding was ineffective, and then periodontal plugs with hemostatic powder were used to barely stop the bleeding. Considering that the patient’s gums were characterized by non-inflammatory extensive bleeding, a consultation with the Department of Hematology was requested to investigate the cause, and early acute leukemia was confirmed by laboratory tests. Gingival bleeding is a common disease in dentistry clinics, and its etiology can be divided into two categories: local factors and systemic diseases. The local causes are: 1.Stimulation of cavity The cavity in the tooth neck is not filled in time, and it is allowed to develop under the gum margin, and after forming brown-black cavity, because of its untidy edge and sharp, it often stimulates the gum and causes the gum ulcer and bleeding. 2.The most common factor is calculus stimulation because the calculus attached to the cervical part of the teeth will constantly stimulate the gums, causing the gums to inflame and bleed. 3, followed by periodontal disease Because of the tissue lesions around the teeth, the gums become edematous and inflamed, the capillaries expand and become congested, and once they encounter stimulation such as chewing or improper brushing, they often cause the gums to bleed. Gum bleeding caused by the above-mentioned common local lesions can be stopped as long as the local lesions are treated promptly and the bleeding is stopped after the inflammation. It is important to note that certain systemic diseases can also cause gum bleeding, such as acute and chronic leukemia, hemophilia (coagulation factor deficiency disease), liver cirrhosis, hypersplenism, etc., which lead to low blood clotting function, and can cause gum bleeding symptoms. Therefore, those who still have gum bleeding after removing local irritants and anti-inflammatory treatment should go to the hematology department for further examination as early as possible to clarify the cause and provide timely treatment to avoid misdiagnosis and misdiagnosis.