Platelet count of 400*10^9/L to 500*10^9/L is already significantly elevated, but the condition is not very serious, but need to be combined with the specific cause of the disease to be treated in a timely manner. The normal value of platelet count ranges from 100 to 300*10^9/L. Elevated platelet count can lead to increased blood viscosity, thus increasing the risk of thrombotic diseases such as cerebral infarction, myocardial infarction, and intravascular thrombosis. The probability of thrombotic complications increases when the platelet count is between 400 and 500*10^9/L, so it should be treated promptly. Elevated platelets can be categorized into secondary platelet elevation and primary platelet elevation depending on the cause. Cerebral hemorrhage, splenectomy and other diseases can be secondary to platelet elevation, which is temporary and can gradually return to normal. Primary thrombocythemia, true erythrocytosis and other myeloproliferative neoplasms can lead to primary platelet elevation, and platelet count can be sustainably elevated. After the diagnosis is confirmed by complete bone marrow aspiration and biopsy, platelet-lowering and anti-platelet aggregation treatments should be provided. It is recommended that the patient should consult the hematology department in time to clarify the cause of platelet elevation and treat the cause of the disease.