OBJECTIVE：To systematically evaluate the efficacy and safety of decitabine monotherapy in the treatment of myelodysplastic syndrome （MDS），and to provide evidence-based reference to the clinic. METHODS ：Retrieved from Embase ， Cochrane Library ，PubMed，Medline，Clinical Key ，Google Scholar ，CNKI，CBM and Wanfang data ，during the inception to Jun. 26th， 2020， randomized controlled trials （RCTs） about decitabine （decitabine group ） versus traditional combined chemotherapy（control group ）in the treatment of MDS were collected. After literature screening and data extraction ，literature quality evaluation with bias risk evaluation tool recommended by Cochrane systematic evaluator manual 5.2.2，Meta-analysis was performed by using Rev Man 5.3 software. RESULTS ：A total of 590 patients with 11 RCTs were included. Meta-analysis results showed that complete remission rate [OR ＝1.82，95％ CI（1.23，2.70），P＝0.003] and total response rate [OR ＝1.54，95％ CI（1.05， 2.27），P＝0.03] of decitabine group were significantly higher than those of control group ；the incidence of ADR [OR ＝0.26，95％ CI（0.16，0.40），P＜0.000 01]，the incidence of infection [OR ＝0.48，95％ CI（0.27，0.85），P＝0.01] and the incidence of myelosuppression [OR＝0.37，95％ CI（0.17，0.81），P＝0.01] in decitabine group were significantly lower than control group. The results of subgroup analysis according to the course of treatment showed that there was no significant difference in the complete remission rate and total response rate between 2 groups in the treatment course of 3 and 4 months（P＞0.05）；but there was significant difference in the treatment course of 1 month or 2 months，the decitabine group was significantly higher than control group（P＜0.05）. CONCLUSIONS：Decitabine has good efficacy and safety in the treatment of MDS patients ，and when the treatment time is less than or equal to 2 months，the complete remission rate and total response rate of decitabine in MDS lis1270755@163.com patients are better.