The classification and count of leukocytes is an important part of routine blood tests, leukocytes mainly include five categories, namely neutrophils, lymphocytes, monocytes, eosinophils, basophils, and a high proportion of monocytes are mainly seen in the following cases: 1, acute infections, monocytes are produced in the mononuclear macrophage system, in the time of infection, the body will generally stress stimulate the mononuclear macrophage system is active, it will release a large number of monocytes. This is a characteristic of acute infections. 2, mainly in the recovery period of acute infectious diseases, for example, during the treatment of certain infectious diseases, the monocytes are higher during the recovery period, which is a sign of good prognosis. 3, the high proportion of monocytes is mainly seen in blood Systemic diseases, such as in leukemia there is a classification called acute monocytic leukemia, mainly abnormal proliferation of monocytes, a large number of cells in the patient’s blood and bone marrow are basically monocytes, primitive and naive monocytes, there are others, such as chronic granulocytic monocytic leukemia, chronic granulocytic leukemia are accompanied by an increase in monocytes.