The proportion of neutrophils in normal adults is 50%-70% and the proportion of lymphocytes is 20%-40%. If there is a decrease in the proportion of neutrophils and an increase in the proportion of lymphocytes, the most common causes are: i. Viral infections, especially acute respiratory viral infections, such as cold virus and rubella virus, will result in a decrease in the proportion of neutrophils and an increase in the proportion of lymphocytes. Second, various physical and chemical factors lead to the suppression of bone marrow hematopoietic function, such as radionuclides and chemical substances cause bone marrow hematopoietic dysfunction, there will be an increase in the proportion of lymphocytes and a decrease in the proportion of neutrophils. In acute lymphocytic leukemia or chronic lymphocytic leukemia, there is an abnormally high lymphocyte ratio and a significantly lower neutrophil ratio due to disorderly proliferation of lymphocytes.