Objective To explore the efficacy and safety of umbilical cord mesenchymal stem cells(UC-MSCs) infusion in treating refractory rheumatoid arthritis(RA).Methods Four cases of refractory RA and invalid by improving disease condition and anti-rheumatic drugs in this hospital from December 2014 to November 2015 underwent once UC-MSCs suspension intravenous infusion after signing the informed consent.The cells number was 1 × 106 per kg.We evaluated the tender and swollen joints number,erythrocyte sedimentation rate(ESR),C-reactive protein(CRP),28-joint disease activity score(DAS28),visual analog scale(VAS)pain score and related safety indices were compared between before and after infusion.Results After infusion treatment in 3 cases,the tender and swollen joints number,ESR and DAS28(4) score were significantly improved,but another case was ineffective.No anaphylaxis,rejection reaction or adverse events occurred in all cases and no abnormal change was found in routine blood,liver and kidney function.Conclusion The UC-MSCs infusion is has good safe for treating refractory RA and improves the disease condition to some extent.