Abstract: Objective To analyze the relationship between neutrophil/lymphocyte(NLR) and risk stratification and prognosis in patients with acute coronary syndrome(ACS), and to assess the prognostic value of NLR combined C-reactive protein(CRP) in patients with ACS. Methods Total 430 patients diagnosed with ACS by coronary angiography in our hospital from October 2018 to July 2019 were selected and followed up by telephone for an average of 10 months. All patients were divided into low NLR group and high NLR group according to median NLR level; low risk group, middle risk group and high risk group according to the scores of GRACE and TIMI; MACE group and Non-MACE according to follow up results. The clinical data between each group were compared and the risk factors of MACE in ACS patients were analyzed. The prognostic value of NLR combined CRP was evaluated by ROC curve. Results The proportion of male patients, serum creatinine, CRP, Gensini scores and the occurrence of MACE in the high NLR group were significantly higher than those in the low NLR group, while the left ventricular ejection fraction(LVEF) was significantly lower than that in the low NLR group(all P<0.05). The NLR level of the high risk group in risk stratification was significantly higher than that in the middle and low risk groups(all P<0.05). The area under the curve(AUC) of NLR predicted the high-risk group in GRACE risk stratification was 0.684(P<0.05). The NLR and CRP levels were significantly higher in the MACE group than those in the Non-MACE group(all P<0.05). Dual logistic regression analysis showed that NLR and CRP were an independent risk factor for the occurrence of MACE in ACS patients(all P<0.05), the ROC curve showed that the AUC of NLR combined with CRP to predict the incidence of MACE was 0.832, the sensitivity was 71%, and the specificity was 87%(P<0.001). Conclusion The level of NLR is significantly associated with risk stratification and prognosis in ACS patients. NLR combined CRP have high predictive value for the occurrence of MACE in ACS patients.