The large platelet ratio (P-LCR) is the proportion of large platelets to the total platelets in the blood, with a normal value of 17.5%-42.3%, but the value may vary due to differences in testing methods and instruments in each laboratory. Platelets are small pieces of cytoplasm shed from the cytoplasm of mature megakaryocytes in the bone marrow. Large platelets are platelets that have not yet been fully transformed into platelets. The large platelet ratio test has some clinical significance in determining bone marrow hematopoietic function, but it does not have definite diagnostic value. For example, a low platelet ratio often indicates a high degree of platelet maturation in the body, which has little effect on the human body. If the large platelet ratio is high, the maturity of platelets is low, which is often seen in primary thrombocytosis, aggregated cell leukemia, etc. However, when there is bone marrow hematopoietic dysfunction, such as aplastic anemia, diffuse intravascular coagulation, acute leukemia disease or chemotherapy or radiotherapy means, the large platelet ratio will be low because the megakaryocytes cannot divide and proliferate normally and cannot produce normal forms of platelets. In this case, the doctor needs to consider the patient’s medical history, clinical symptoms and other auxiliary examinations, and take appropriate treatment after diagnosis, and the large platelet ratio will gradually return to normal.