There are many diseases that cause thrombocytopenia clinically, and the common ones are primary thrombocytopenic purpura, aplastic anemia, acute leukemia, and hypersplenism. 1. Primary Thrombocytopenic Purpura: It is an autoimmune disease caused by a variety of complex mechanisms. The patient’s cellular immunity and humoral immunity are abnormal, resulting in an attack on his own platelets, leading to excessive platelet destruction and decreased platelet production, resulting in thrombocytopenia, and the main symptom is bleeding from the skin and mucous membranes. 2. Aplastic anemia: it is a bone marrow hematopoietic failure caused by many reasons, mainly the production of blood cells is impaired, resulting in a decrease in whole blood cells, including platelets. Common symptoms are anemia, bleeding and infection. 3. Acute leukemia: it is an abnormal malignant proliferative disease of hematopoietic stem cells. The abnormal proliferation inhibits normal hematopoiesis of bone marrow, which can lead to thrombocytopenia. 4. Hypersplenism: The spleen is an important immune organ and can eliminate useless or abnormal blood cells in the body. When hypersplenism occurs, it attacks normal blood cells as well, leading to pancytopenia. Thrombocytopenia is found on examination, further examination should be carried out to clarify the cause of the disease and then actively treat it so as not to miss the condition.