Objective To evaluate the efficacy of n-3 PUFAs (fish oil) for prevention of cardiovascular events. Methods Randomized controlled trials (RCTs) were searched from the following electronic databases: PubMed, EMbase, The Cochrane Library (Issue 1, 2009), CBM, and CNKI. Quality assessment and data extraction were conducted by two reviewers independently. Disagreement was resolved through discussion. All data were analyzed by using Review Manager 4.2 software. Results Five studies involving 37 689 participants met the inclusion criteria. Meta-analysis results showed that: 1) Compared with placebo, the incidence rates of the cardiovascular death (RR=0.91, 95% CI 0.84 to 0.98), cardiovascular events (RR=0.95, 95%CI 0.91 to 0.98), angina (RR=0.79, 95%CI 0.64 to 0.96), and myocardial infarction (RR=0.79, 95%CI 0.65 to 0.96) could be reduced by n-3 PUFAs (fish oil). 2) There were no significant differences in death from any cause, the hospitalization rates of cardiovascular disease, sudden death, and heart failure (RR=0.95, 95%CI 0.90 to 1.00; RR=0.97, 95%CI 0.93 to 1.02; RR=0.90, 95%CI 0.79 to 1.01; RR=0.98, 95%CI 0.91 to 1.06). 3) Compared with placebo, the incidence rates of the arrhythmia and stroke could be increased, but there were no significant differences (RR=1.14, 95%CI: 0.80 to 1.62; RR=1.12, 95%CI 0.97 to 1.30). Conclusion Compared with placebo, n-3 PUFAs (fish oil) has good effects on reducing the incidence rates of total cardiovascular events, cardiovascular death, myocardial infarction, and angina pectoris, and it has the same efficacy in death from all cause, sudden death, heart failure, and the hospitalization rates of cardiovascular disease. There are no significant differences in the increased rates of arrhythmia and stroke.