Platelet distribution width is an indicator of the dispersion of platelet volume size in peripheral blood. Under normal circumstances, the decrease in platelet distribution width indicates that the platelet volume in the peripheral blood is more uniform in size, and the difference in size is not big. This situation can be seen in some normal people, mainly in patients with reduced hematopoietic function, such as patients with aplastic anemia due to bone marrow hematopoietic failure, the body’s hematopoietic stem cells can not proliferate and divide normally, which leads to the megakaryocytes can not produce platelets of various sizes, and can only produce a small amount of small platelets, and the difference in the distribution of these small platelets is not big. As a result, megakaryocytes cannot normally produce platelets of various sizes, but only a small number of platelets of small size can be produced, and these platelets of small size do not differ much from each other, which results in a decrease in the width of platelet distribution. After treatment, the condition of patients with remission, megakaryocytes restore the normal function of platelet production, they will produce platelets of various sizes, and the situation of reduced platelet distribution width will be significantly improved.