Objective To investigate the peripheral blood neutrophil to lymphocyte ratio(NLR) for the early diagnosis of acute coronary syndrome(ACS) .Methods A total of 247 patients with suspected ACS and chest pain ,including 51 cases with acute ST segment elevation myocardial infarction(STEMI) ,42 cases with acute non‐ST segment elevation myocardial infarction(NSTEMI) , 87 cases with unstable angina pectoris(UA) and 67 cases with non‐cardiogenic chest pain(NCCP)were enrolled and detected for white blood cells count and classification .The sensitivity ,specificity ,positive predictive value ,negative predictive value ,receiver op‐erating characteristic(ROC) curve of NLR were analyzed .Results Among all patients ,the most common was UA ,followed by NC‐CP ,STEMI and NSTEMI .Level of neutrophil proportion and white blood cell count were lowest in NCCP group ,followed by UA , NSTEMI and STEMI group ,but lymphocyte proportion was with the opposite change tendency .Diagnostic sensitivity ,specificity , accuracy ,positive predictive value and negative predictive value of NLR for ACS were higher than white blood cell count .Conclusion NLR was with various advantages for the early diagnosis ,prognosis evaluation and state of ACS .