Platelets are cells, which are blood cells with hemostatic function in the human body. Normal platelet cytosol is round, or some are oval or irregular in shape, with a diameter between 2-3 cm and a light blue cytoplasm. The normal range of platelet count is 100000-300000/ml, the main function of platelet is to stop bleeding, when platelet count decreases, the body’s hemostatic function will be reduced, and patients often have bleeding symptoms. Thrombocytopenia is very common in clinical practice, and common diseases include aplastic anemia, acute leukemia, myelodysplastic syndrome, and primary thrombocytopenic purpura. Thrombocytosis is also very common, and common diseases include myeloproliferative disorders such as primary thrombocytosis, true erythrocytosis, and chronic granulocytic leukemia. In chronic granulocytic leukemia, there is a progressive increase in the number of platelets as the disease progresses.