Lymphocytopenia is a very common clinical phenomenon. It is mainly caused by the phenomenon of bone marrow suppression when tumor patients undergo drug chemotherapy, which can cause a decrease in lymphocyte production. Patients are prone to immune deficiency and combined viral or bacterial infections. Lymphocytes belong to the immune organs of the body and have strong ability to kill viruses and bacteria. Once the body is combined with serious infections, such as acute severe pancreatitis and acute suppurative obstructive cholangitis, it will cause a large consumption of lymphocytes and a decrease in lymphocytes. In addition, patients with cirrhosis and hypersplenism can cause the destruction of blood cells, thus causing lymphocytopenia, and HIV in AIDS patients can cause the destruction of lymphocytes, resulting in lymphocytopenia.