Objective To compare the clinical efficacy of luteal phase support with oral dydrogesterone tablets and vaginal progester-one gel combined with oral dydrogesterone tablets during hormone replacement therapy-frozen embryo transfer(HRT-FET).Methods A retrospective analysis was conducted on a total of 489 cycles which underwent HRT-FET at the Center of Reproductive Medicine,the University of Hong Kong-Shenzhen Hospital from November 2018 to June 2022.There were 226 cycles underwent with oral dydrogester-one tablets as luteal support,and 263 cycles underwent with vaginal progesterone gel combined with oral dydrogesterone tablets as luteal support.The primary observation index was the delivery rate.The pregnancy outcomes of HRT-FET in the two groups were compared and analyzed,and the related factors were analyzed.Results There were no significant differences in the age,body mass index,number of antral follicles,total number of eggs,serum levels of estradiol and progesterone on the second day of the menstrual cycle and the day before endometrial transformation between the two pregnant women(P＞0.05).There were also no significant differences in the abortion rate,ectopic pregnancy rate,biochemical pregnancy rate,clinical pregnancy rate,delivery rate,and neonatal weight between the two groups(P＞0.05).In the second day of cleavage stage embryo transfer subgroup,there were no significant differences in the abortion rate,ectopic pregnancy rate,biochemical pregnancy rate,clinical pregnancy rate,delivery rate,and neonatal weight between the two groups(P＞0.05),and in the fifth day of blastocyst transfer subgroup,there were also no significant differences in abortion rate,ectopic pregnancy rate,biochemical pregnancy rate,clinical pregnancy rate,delivery rate between the two groups(P＞0.05),and in the oral dydrogesterone tablets group,the neonatal weight was significantly higher than that of the vaginal progesterone gel combined with oral dydrogesterone tablets,and the difference was statistically significant(P＜0.05).The multivariate Logistic regression analysis showed that different luteal support protocols had no significant impact on the delivery rate(OR=0.703,95％CI:0.461-1.062,P=0.09).Conclusion There were no significant differences between oral dydrogesterone tablets and vaginal progesterone gel combined with oral dydrogesterone tablets in clinical pregnancy rate and delivery rate during HRT-FET.Therefore,the use of oral dydrogesterone tablets a-lone can be a new option for luteal support in HRT-FET.