Objective To investigate the correspond of microsatellite instability (MSI) on the prognosis and the effect of chemotherapy for colorectal cancer.Methods The publications about the MSI of colorectal cancer from January 2011 to October 2012 were searched.The Web of Knowledge and MEDLINE (PubMed) databases were used for searching English articles.The CNKI and WanFang databases were used for searching Chinese articles.Statistical analysis and graphics were performed with Comprehensive Meta Analysis V2 software.Results Thirty papers were included in this study.For the prognostic Meta-analysis,MSI-H was a protective factor for the overall survival of patients (OR =0.634,0.558-0.720; P ＜ 0.001).Simultaneously,MSI-H was a protective factor for the disease-free survival of patients (OR =0.571,0.479-0.681; P ＜ 0.001).After using of 5-Fu,the survival rate of MSS/MSI-L patients could be significantly elevated (OR =0.515,0.433-0.611; P ＜ 0.001).However,the survival rate of MSI-H patients did not increase significantly (0.631,0.302-1.318; P =0.220).Conclusions Both the overall survival and disease-free survival of MSI-H patients were significantly better than that of MSS/MSI-L patients.For MSS/MSI-L patients,the chemotherapy effect was remarkable.However,for MSI-H patients,there was no statistics difference between chemotherapy and no-chemotherapy group.