The main clinical symptoms of acute leukemia: fever from infection, bleeding, anemia, and enlarged lymph nodes and liver and spleen. 1. Infection: it is one of the most common causes of death in acute leukemia. Infection mechanisms are: ① neutrophil number reduction and functional defects; ② immunodeficiency; ③ skin and mucous membrane barrier destruction; ④ nosocomial infection. 2. Bleeding: 40%~70% of patients have bleeding tendency at the onset. Bleeding mechanisms include: ① thrombocytopenia; ② vascular wall damage; ③ coagulation disorders; ④ increase in anticoagulant substances. 3. Anemia: about 2/3 of the patients have moderate anemia at the time of diagnosis. Anemia mechanisms include: ① abnormal cloning of leukemia cells; ② ineffective erythropoiesis; ③ hemolysis. 4. Lymph nodes and hepatosplenomegaly. When the above symptoms appear, it is necessary to go to the hospital at the first time, to clarify the cause of the disease under the guidance of physicians, and to treat the disease in time.