Objective To evaluate systematically the preventive effect of hydration therapy on contrast induced nephropathy ( CIN ) . Methods The databases of Cochrane Library, PubMed, MEDLINE, WanFang, VIP, CNKI and Embase were retrieved from Jan. 1998 to May, 2012. The quality of randomized controlled trials was identified and assessed according to Jadad quality scoring, and evaluated systematically by using RevMan5.0 software. Results There were totally 137 related documents retrieved initially and 11 documents included involving 1683 patients in 11 trials. The results of systematic evaluation showed that hydration therapy could prevent the occurrence of CIN ( OR =0.27, 95% CI 0.19-0.38, P 0.05). Conclusion Hydration therapy has significant preventive effect on the occurrence of CIN.