The normal value of normal platelet count is 100×10^9/L~300×10^9/L. High platelet count in pediatrics is considered to be related to infectious diseases, iron deficiency anemia, primary thrombocythemia and so on. 1. Infectious diseases: When there are infectious diseases in children, such as upper respiratory tract infection, meningitis, pneumonia, etc., it may cause increased platelet reactivity, which usually returns to the normal range gradually after the condition is controlled. 2. Iron deficiency anemia: the disease is related to insufficient or excessive loss of iron intake, when the body reduces hemoglobin synthesis, platelet high phenomenon may occur. Some children may have no obvious symptoms, but some may have pale skin, dizziness, poor concentration and other symptoms. 3. Primary thrombocythemia: the disease will cause some children with high platelets, mainly due to the clonal proliferation of a single abnormal pluripotent stem cell. When children are sick, they will have spontaneous bleeding, splenomegaly, weakness and other symptoms. It is recommended that children with high platelet counts undergo further detailed examination in order to identify the cause of the disease and then follow the doctor’s instructions for treatment.