A high monocyte ratio in lung cancer patients is generally not serious. Monocytes are involved in the body’s defense system, and a high monocyte ratio indicates that the body’s immunity has been lowered, and should be alerted to the possibility of infections and deterioration of the disease. Monocyte is a kind of white blood cell in human body, which can participate in the defense of human body through phagocytosis and antibody production. Lung cancer patients are susceptible to infections due to decreased immunity and decreased functions of tissues and organs, so the proportion of monocytes, leukocytes and other immune cells often increases, which is a normal performance. The proportion of monocytes to normal leukocytes is 20%-40%. When this proportion is only a little bit higher, it will not affect the body too much, but if the monocyte ratio continues to rise and deviates from the normal value, attention should be paid to the fact that other causes of monocyte elevation or aggravation of the original disease may have occurred. Lung cancer patients with elevated mononuclear cell ratio should go to regular hospitals to consult doctors, conduct all-round examination, and make judgment by combining clinical conditions.