Objective:To compare the clinical outcomes between fresh blastocyst transfer with vitrified-thawed blastocyst transfer. Methods:From 2009 to 2011,874 cases of blastocyst transfer cycles were performed in our center,including 280 cases of fresh blastocyst transfer (group A),and 594 cases of vitrified-thawed blastocyst transfer (group B). Meanwhile a retrospective analysis was performed on the two groups by comparing clinical pregnancy rate,implantation rate,pregnancy outcomes and neonatal status. Results:①The number of transferred embryos in group A(1.88 ± 0.47) was higher than that of group B(1.70 ± 0.53),and the clinical pregnancy rate and implantation rate of group A was significantly lower than that of group B(43.93%,24.96% and 55.39%,40.51%,respectively,P < 0.05). ②No statistical differences were found in the rate of abortion,premature delivery rate,gestational age,pregnancy rate and multiple pregnancy rate in group A(13.82%,32.46%,265.49 ± 14.45d,70.16%,29.84%,respectively) and group B(16.72%,33.84%,264.43 ± 16.08 d,71.86%,28.14%,respectively). In group B,there was only one case of ectopic pregnancy,while no ectopic pregnancy in group A. ③There were no statistical differences in macrosomia,growth restriction and the rate of birth defect between group A(6%,19.66%,1.7%,respectively)and group B(9.4%,17.82%,0.9%,respectively). Conclusion:Vitrified-thawed blastocysts transplantation significantly improved blastocyst implantation rate and pregnancy rate,and did not increase neonatal birth defects,miscarriage,premature delivery rate,and there was no increase of macrosomia and neonatal growth restriction ratio at birth. Therefore,vitrified-thawed blastocysts transfer is an effective and safe protocol in ART practice.