OBJECTIVE：To systematically evaluate the effectiveness and safety of low-m olecular-weight heparin combined with progesterone in the treatment of repeated implant failure （RIF）in embryo transfer patients ，and to provide reference for clinical use of it. METHODS ：Retrieved from Cochrane library ，PubMed，Embase，CNKI and Wanfang database ，randomized controlled trail （RCT）or observational study about low-molecular-weight heparin combined with progesterone （trial group ）versus progesterone（control group ）for RIF patients were collected during the inception to Jul. 2020. After data extraction of studies met included criteria ，the Cochrane 5.1.0 bias risk assessment tool and the Newcastle-Ottawa Scale evaluation scale were used to evaluate the quality of RCTs and observational studies. Rev Man 5.3 software was used for Meta-analysis. RESULTS ：A total of 15 studies were included ，including 10 RCTs and 5 observational studies ，with a total of 2 353 patients. Results of Meta-analysis showed that the implantation rate [RR ＝1.41，95％CI（1.24，1.60），P＜0.01]，pregnancy rate [RR ＝1.38，95％CI（1.23，1.56）， P＜0.01]，live birth rate [RR ＝1.41，95％CI（1.19，1.67），P＜0.01] of trial group were significantly higher than those of control group，with statistical significance ；while the abortion rate [RR ＝0.54，95％ CI（0.33，0.86），P＝0.01] of trial group was significantly lower than that of control group ，with statistical significance. The results of subgroup analysis showed that the implantation rate [RR ＝2.38，95％CI（1.31，4.31），P＝0.004] and pregnancy rate [RR ＝2.58，95％CI（1.62，4.11），P＜0.001] of patients over 35 years old in trial group were higher than control group ，with statistical significance. The main ADR of 2 groups were a small amount of bleeding and ecchymosis at the injection site. No severe ADR was observed. CONCLUSIONS： Low-molecular-weight heparin combined with progesterone can improve the embry o implantation rate ， pregnancy rate and live birth rate of RIF patients ，reduce the abortion rate ，with good safety.