The normal value of platelet count in blood routine is usually (100-300) x 10^9 cells/L, and the specific normal value is also related to the laboratory equipment and so on. Platelet count has very important reference significance in clinical diagnosis and treatment of diseases. 1.Decreased platelet count may lead to prolonged bleeding time and bleeding in severe cases. When the platelet count <20×10^9/L, prophylactic platelet transfusion is needed, and strict bed rest and avoiding trauma. Thrombocytopenia is mostly seen in aplastic anemia, primary immune thrombocytopenia and other diseases. 2. Increased platelet count i.e. platelet count > 400 x 10^9/L. Thrombocytosis has an increased risk of thrombosis. Splenectomy may be helpful in some thrombocytosis conditions. Thrombocytosis is seen in some myeloproliferative disorders such as primary thrombocythemia.