Thrombocytopenia is to look at the indicator of platelet count in the routine blood test. Routine blood test is the most basic blood test, can observe the white blood cells, red blood cells, platelets and other indicators of high and low. The normal value of platelets is generally 100,000 to 300,000/mm^3, below 100,000 can be called thrombocytopenia. There are many causes of thrombocytopenia, so when thrombocytopenia occurs, it is necessary to combine clinical manifestations, medical history, physical examination and other examinations to help determine the cause, such as peripheral blood smear, anti-platelet antibodies, fibrinogen, HIV (AIDS), HCV (hepatitis C), HBV (hepatitis B) serology, vWF lytic protease, bone marrow aspiration and so on. For those who suspect lymphoproliferative disorders, rheumatism, antiphospholipid syndrome, etc., additional appropriate laboratory tests are required. If thrombocytopenia is diagnosed, early identification of the cause and standardized treatment are recommended to minimize the adverse effects of the disease.