The reference value of lymphocytes in normal adults is (0.8 to 4) × 10*9/L. If the absolute value of lymphocytes is higher than this reference value, it is called high absolute value of lymphocytes. Lymphocytes are the main immune cells in the body, and observing changes in their number can help to understand the immune function status of the body. The number of lymphocytes is influenced by both physiological and pathological factors, so the main reasons for high absolute lymphocyte values are the following: Physiological lymphocytosis is mainly higher in the afternoon and evening than in the morning, and the proportion of lymphocytes in infants after 1 week of life can be more than 50%, which can last for 6-7 years and then gradually decrease to adult levels. Pathological lymphocytosis is mainly seen in infectious diseases and mainly viral infections, such as: measles, chickenpox, mumps, viral hepatitis, infectious mononucleosis, epidemic hemorrhagic fever, but also in tuberculosis, whooping cough, syphilis, etc. The number of lymphocytes increases in these conditions, as does the percentage. In addition, lymphocytosis can also occur in a variety of lymphomas (including chronic lymphocytic leukemia, acute lymphocytic leukemia, and some lymphomas), during recovery from acute infectious diseases, and after transplant rejection. Clinically, a high absolute lymphocyte value alone is not a definitive diagnosis of disease, but rather a diagnosis of the appropriate disease because of the combination of the patient’s other clinical symptoms and relevant laboratory tests to exclude physiological lymphocytosis.