Abstract: Objective To investigate the value of color ultrasound Doppler (CDFI) and contrast-enhanced ultrasound (CEUS) parameters in assessing endometrial receptivity in patients undergoing in vitro fertilization and embryo transfer (IVF-ET). Methods Eighty-six patients with IVF-ET in our hospital from June 2016 to June 2018 were analyzed. According to whether they reached clinical pregnancy, they were divided into pregnancy group (32 cases) and unsuccessful group (54 cases). The pulsatility index (PI) and resistance index (RI) of the endometrial CDFI and the CEUS index between the rise time (RT), peak time (TTP), peak intensity (PI), and area under the curve (AUC) were compared between the two groups. Differences were analyzed to investigate the correlation between different ultrasound parameters and endometrial micro-vessel density (MVD), and to compare the predictive power of different ultrasound parameters for pregnancy success. Results The CDFI-PI and RI and CEUS-RT and TTP in the endometrium of the pregnant group were significantly lower than those in the unsuccessful group, while CEUS-PI was significantly higher than the unsuccessful group (all P<0.05). There was no statistical difference between the groups of CEUS-AUC (P>0.05). The MVD of the pregnant group was significantly higher than that of the unsuccessful group (P<0.05). Correlation analysis showed that PI and RI of CDFI, CEUS RT and TTP were negatively correlated with endometrial MVD and positively correlated with CEUS PI. In predicting pregnancy outcomes, CEUS-PI has the highest area under the curve, followed by CDFI-PI and RT, and lower TTP and RI. The optimal cut-off value of CEUS-PI for predicting clinical pregnancy is ≥4.75 dB, with a predictive sensitivity of 68.75% and a specificity of 92.59%. Conclusion The peak intensity of endometrial contrast-enhanced ultrasound is positively correlated with the micro-vessel density. The use of CEUS-PI to predict IVF-ET pregnancy outcome has a high diagnostic specificity.