There are many causes of platelet elevation in children. First, the most common is reactive platelet elevation, such as some infections, including respiratory tract infections, urinary tract infections or gastrointestinal tract infections, central nervous system infections, etc., which can lead to reactive platelet elevation. Second, caused by a variety of anemia, the most common is nutritional iron deficiency anemia, this child due to anemia, bone marrow proliferation is more active, will also appear platelet increase. Thirdly, primary thrombocytosis, the cause of which is generally unclear. Thrombocytosis refers to platelets exceeding 450×10^9/L and platelets exceeding 600×10^9/L, which need to be treated with anticoagulant drugs.