Objective To explore the diagnostic values of contrast enhanced ultrasound（CEUS） on difficult cases of cesarean scar pregnancy. Methods CEUS was performed on 24 patients underwent ultrasound examination that revealed the relationship between gestational sac and cesarean scar was closed, but the images of US were atypical and the accurate differential diagnostic was hard to make. The diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Youden index of conventional ultrasound and CEUS, according to the result of surgery and pathology were observed. Results The diagnostic accuracy of conventional ultrasound was 75.00%, Sensitivity was 88.24%, Specificity was 85.71%, PPV was 93.75%, NPV was 75.00%, Youden index was 73.95%, while the diagnostic accuracy of CEUS was 100%. CEUS corrected the diagnostic result of conventional ultrasound in 6 cases (25.00%). There was significantly difference of the diagnosis accurate rate between these two methods （P＜0.05）. Conclusion CEUS can provide more accurate diagnostic information. Its diagnostic accuracy is higher than that of conventional ultrasound, and it has great clinical value.