Low absolute lymphocyte values are seen as a manifestation of low immunity, but are not limited to low immunity. Normal absolute value of lymphocytes is (0.8~4)×10^9/L. There are many reasons for low lymphocytes, besides low immunity, it is also related to the application of adrenocorticotropic hormone, alkylating agent, anti-lymphocyte globulin and other treatments, as well as radiation damage, T-lymphocyte immunodeficiency disease, and gammaglobulin deficiency (B-lymphocyte immunodeficiency), and so on. When a patient’s absolute value of lymphocytes is low, the patient should not judge or diagnose on his own based on the results of a single test, but should consult a doctor in time, who will analyze and diagnose the case according to the specific circumstances.