Acute coronary syndrome (ACS) is a serious type of coronary heart disease, which has high morbidity rate and mortality rate. Inflammation plays an important role in the initiation and development of ACS. In clinical practice, monitoring inflammation related factors is conducive to risk stratification and prognosis evaluation of ACS patients. Some studies have shown that leukocyte differential count may be one of the reliable inflammatory markers for clinical evaluation of prognosis in patients with ACS. This article reviews the research progress of leukocyte differential count in predicting the prognosis of ACS.