The absolute value of neutrophils is less than 1.5×10∧9/L, which is considered to be a decrease in neutrophil value. Low neutrophil value is mainly caused by low neutrophil production, increased destruction and abnormal distribution of neutrophils. 1. The causes of neutropenia are chemotherapeutic drugs or non-steroidal drugs, as well as aplastic anemia and leukemia, which can lead to neutropenia. 2. Increased destruction or consumption of neutrophils is common in hypersplenism or autoimmune diseases such as systemic lupus erythematosus; and various viral infections, typhoid fever, hepatitis. 3. Abnormal distribution of neutrophils can be seen in pseudogranulocytopenia, endotoxemia. Neutrophil is an important line of defense in the human body. If the neutrophil is mildly decreased but greater than 1.0×10∧9, if there is no clinical symptom, it can be temporarily observed and regular rechecking of blood routine; if it is lower than 1.0×10∧9, it is necessary to go to the hospital for further examination and diagnosis for further treatment.