Abstract: Objective To assess the clinical effectiveness and safety of low-dose decitabine compared with best supportive care for intermediate- or high-risk myelodysplastic syndrome (MDS). Methods The related documents were searched on the PubMed, Embase, Cochrane Library, CNKI, and CBM databases from 1995 to 2012. Randomized controlled trials (RCTs) about Low-dose decitabine alone or combined with best supportive care for MDS were retrieved. The methodological quality of the included studies was assessed according to the Cochrane Reviewer's Handbook. Meta-analyses were performed using RevMan 5.0 software. Results Three RCTs involving 984 patients with MDS were included. Results of Meta-analysis showed that significant differences were found in overall response（OR）OR=22.9,95%CI(7.51，69.85)，P＜0.00001, partial response (PR)OR=17.23,95%CI(2.27，130.76)，P=0.006，hematology improve（HI） OR=3.21，95%CI(1.53，6.75)，P=0.002，median survival time 13.5 vs. 7.3 months, P＜0.05, grade 3 or 4 febrile neutropenia OR=4.85,95%CI(2.55，9.21)，P＜0.00001，but not in complete remission （CR）OR=6.39，95%CI(0.25，166.49)，P=0.26, grade 3 or 4 thrombocytopenia OR=2.35，95%CI(0.63， 8.69)，P=0.2 between DEC and BSC regimen. Conclusion The low-dose decitabine can improve overall response, partial response and Hematology improve；however，it also increases grade 3 or 4 febrile neutropenia.