Objective To investigate the efficacy of N-acetylcysteine on prevention of contrast -induced nephropathy (CIN).Methods According to the regulation of evidence-based medicine,the selection criteria,elimination criteria and search strategy were defined.PubMed,Cochrane Library,Wiley Online Library and Google Scholar were searched.The literature limited range was from January 2000 to December 2011.Two investigators extracted the data independently from all the studies that accorded with selection criteria using a suitable form.All the statistical analyses were performed with RevMan version 5.1.Results A total of 151 potential literatures were screened and 16 remained literatures (including 4588 patients) were identified to accord with the criteria in this meta-analysis.In 14 literatures,the Jadad score was 3 at least.The meta-analysis of 16 trials showed N-acetylcysteine could prevent CIN from happening [odds ratio (OR)=0.65,95％ CI 0.46-0.92,P=0.01].In the groups of average Scr baseline ＜ 132.6 μmol/L,result displayed the OR of incidence associated with Nacetylcysteine for prevention of CIN was 0.93 (95％ CI 0.75-1.15,P=0.49).In the groups of average Scr baseline ≥ 132.6 μmol/L,the OR for N-acetylcysteine associated with incidence of CIN was 0.52 (95％ CI 0.30-0.93,P=0.03).Conclusion There is specific effect that N-acetylcysteine prevents CIN from happening in the groups of average Scr baseline ≥ 132.6 μmol/L.