Objective To study the effects of oxytocin antagonists-atosiban on pregnancy outcome after thaw embryo transfer (TET).Methods Between Jul.and Dec.2012,a total of 120 women undergoing TET in Reproductive Medical Center,General Hospital of Tianjin Medical University were randomly allocated into atosiban and control group.They were all transferred 2 or 3 top quality embryos at phase of 7-8 cells.Patients in atosiban group were administered by intravenous administration of atosiban before 30 minutes of embryo transfer with a total administered dose of 37.5 mg.In the control group,no special treatment was given before embryo transfer.All patients in 2 groups underwent progesterone luteal support regularly after embryo transfer,then the clinical rate of pregnancy,implantation and early abortion was compared.Results The clinical pregnancy rate per cycle and implantation rate per transfer were 60％(36/60) and 30.0％ (48/160) in the atosiban group,which were higher than 42％ (25/60) and 20.3％ (31/153) in the control group (all P ＜ 0.05).Early abortion rate was 6％ (2/36)in the atosiban group,which was no statistical difference comapring with control group [16％ (4/25),P ＞ 0.05].Conclusion It was suggested that atosiban treatment before embryo transfer can improve the outcome of pregnancy,and increase clinical pregnancy rate and implantation rate after TET.