Aim To investigate the relationship between neutrophil/lymphocyte ratio (NLR) and severity of coronary artery stenosis and cardiovascular end point events after percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS). Methods A total of 302 patients admitted to our hospital with coronary angiography and PCI were enrolled in this study. All patients were divided into two groups according to Gensini scores:low score group (≤46.5 points) and high score group (＞46.5 points). The groups were compared according to their NLR and other parameters. All patients were divided into two groups according to the occurrence of cardiovascular end point events:event group and non-event group. The ROC curve was used to analyze the predictive value of NLR in cardiovascular end point events after PCI in patients with acute coronary syndrome. Results The prevalence of hypertension, lower high density lipoprotein cholesterol and NLR in the high score group were higher than those in the low score group (P＜0.05). Binary stepwise Logistic regression analysis showed that NLR and high density lipoprotein cholesterol were independent predictors of severity of coronary artery disease. The rates of elderly patients (≥60 years), hypertension, diabetes, lower high density lipoprotein cholesterol and NLR in the event group were higher than those in the non-event group (P＜0.05). The ROC curve analysis showed that the area under the curve of NLR in predicting cardiovascular end point events of PCI patients was 0.710 (95%CI was 0.632～0.788, P＜0.05). When the cut off value of NLR was 3.985, the diagnostic efficiency was the highest, with a sensitivity of 67.3% and a specificity of 70.4%. Kaplan-Meier curve analysis showed that the incidence of cardiovascular end point events were significantly higher in NLR＞3.985 group than in NLR＜3.985 group.Multivariate COX regression analysis showed that NLR, elderly, hypertension and diabetes were independent predictors of cardiovascular end point events after PCI. Conclusion The high NLR value may be an independent predictor of the severity of coronary artery stenosis and the incidence of cardiovascular end point events after PCI.