Objective To analyze the value of neutrophils/lymphocytes ratio (NLR) on predicting the cardiovascular events at hospital discharge and ≥ 12 months follow-up for patients with ST-segment elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI) by meta-analysis.Methods Both English and Chinese databases,including PubMed,EMBASE,Wanfang database from their reception to June 2014 were searched to identify randomized controlled studies or non-randomized controlled studies that reported relationship between NLR and the prognosis of patients with STEMI undergoing PCI.The Newcastle-OttawaScale (NOS) system was employed to assess the quality of literatures enrolled in this study.Two reviewers assessed the quality of each trial and extracted data independently.A standardized form and RevMan 5.2 software were used to extract information,and perform quantitative analysis,respectively.Results A total of 1 953 patients from 6 clinical trials were included in this meta-analysis.The risks of all-cause mortality (RR:0.29,95％ CI:0.19-0.46,P ＜ 0.001),major adverse cardiac events (RR:0.38,95％ CI:0.31-0.46,P ＜ 0.001),nonfatal myocardial infarction (RR:0.43,95 ％ CI:0.28-0.67,P ＜ 0.001),stent thrombosis (RR:0.32,95 ％ CI:0.19-0.53,P ＜ 0.001),and TIMI flow after PCI procedure ＜ 3 grade (RR:0.34,95％ CI:0.14-0.86,P =0.020) were significantly lower in patients with NLR ≤3.30 compared patients with NLR ＞ 3.30 at hospital discharge.During ≥ 12 months follow-up,the risks of death (RR:0.33,95％ CI:0.23-0.45,P ＜ 0.001),major adverse cardiac events (RR:0.27,95 ％ CI:0.20-0.35,P ＜ 0.001) were significantly lower.Whereas nonfatal myocardial infarction was not significantly different (RR:0.42,95％ CI:0.05-3.45,P =0.420) in patients with NLR≤3.30 compared patients with NLR ＞ 3.30.Conclusions Results from this meta-analysis show that the NLR could predict short-and long-term prognosis in patients with STEMI undergoing PCI.This finding needs to be validated by large-scale clinical trials in the future.