Objective To analyze the changes of estrogens before and after artificial cycle frozen embryo transfer (FET) and their relationship with treatment outcomes.Methods A total of 105 patients undergoing artificial cycle FET were enrolled from January 2021 to January 2022. According to pregnancy outcomes after treatment, they were divided into pregnancy group (47 cases) and non-pregnancy group (58 cases). Before and after FET, levels of estrogen ［estradiol (E2), progesterone (P)］ and endometrial blood flow parameters were detected. The predictive efficiency of estrogens for pregnancy outcomes was evaluated by ROC curves. The relationship between estrogens and endometrial blood flow parameters was analyzed by Pearson correlation analysis. Results The levels of serum E2 and P in pregnancy group were significantly higher than those in non-pregnancy group (P<0.05). After FET, there was no significant difference in VI between the two groups (P>0.05), but FI and VFI in pregnancy group were significantly higher than those in non-pregnancy group (P<0.05). AUC of E2 at 7d after FET for predicting pregnancy outcomes was 0.929, significantly better than that before FET (0.860) and at 14d after FET (0.839) (P<0.05). AUC of P at 7d after FET for predicting pregnancy outcomes was 0.793, without significant difference compared with that before FET (0.823) and at 14d after FET (0.746) (P>0.05). The levels of serum E2 and P at 7d after FET were negatively correlated with uterine VI level at 1d after FET, while positively correlated with FI and VFI levels (P<0.05). Conclusion The levels of estrogens significantly increase after artificial cycle FET. Serum E2 and P have good predictive value for pregnancy outcomes