The causes of hemolysis include erythrocyte factors and extra-erythrocyte factors. 1. Hemolysis caused by red blood cell factors can be seen in red blood cell membrane abnormality, red blood cell enzyme abnormality, red blood cell hemoglobin abnormality and so on. (1) Hemolysis caused by abnormalities of erythrocyte membrane mainly includes hereditary elliptocytosis and hereditary spherocytosis. (2) Hemolysis caused by erythrocyte enzyme abnormalities mainly include serosanguineous disease and pyruvate kinase deficiency. (3) Hemolysis caused by abnormal hemoglobin in red blood cells can be seen in thalassemia and hemoglobinopathies. 2. Hemolysis caused by extra-erythrocytic factors can be seen in poisoning, high fever, infection, hypersplenism, lupus and other immune diseases. (1) Poisoning, infection, high fever and other diseases may affect the structure of red blood cell membrane and cause hemolysis. (2) Hypersplenism may cause mechanical destruction or phagocytosis of red blood cells in the spleen. (3) Immune diseases may produce immune-mediated hemolysis. In conclusion, hemolysis has many causes and is a relatively serious disease, which may lead to anemia, liver and kidney failure and other serious consequences, and requires prompt medical attention for diagnosis and treatment.