The clinical significance of high mean platelet volume is to observe the presence or absence of bleeding tendency, the presence or absence of changes in bone marrow hematopoietic function, as well as for the diagnosis and treatment of some diseases. The normal value of mean platelet volume is 7~11fl, when the mean platelet volume is out of the normal range, it is called high mean platelet volume. Clinically, the patient’s clinical condition is usually determined by the mean platelet volume parameter (MPV) in conjunction with the platelet count (PLT). For example, after myelofibrosis and splenectomy, there is an increase in mean platelet volume and a normal platelet count. In acute myocarditis, an increase in mean platelet volume is accompanied by a decrease in platelet count. When there is a high mean platelet volume, patients should go to the hospital in time, and do the next examination and treatment under the guidance of the doctor.