Objective To compare and analyze the ultrasonographic images and clinical characteristics of undifferentiated embryonal sarcoma（UES）and Hepatic mesenchymal hamartoma （HMH），and to investigate the differential performance. Methods 19 cases of UES (UES group)and 25 cases of (HMH group) patients confirmed by pathologically in our hospital were collected, and everyone underwent ultrasonography. Analyze the differences in ultrasonographic and clinical features. By binary Logistic regression analysis，the statistically significant indicators were bring into the receiver operating characteristic (ROC) curve and the differential performance of every feature was evaluated. Results There were no statistically significant differences in site，proportion of cystic-solid complex and size between the two groups，but there were significant differences in homogeneity of echo，thick-walled cystic，bleeding and age （all P＜0.05）.In UES，the solid component is often inhomogeneous and complex hypoechoic. The cyst was multilocular，with irregular and no tension. While the HMH solid region is usually homogeneous and hyperechoic，with regular cavity and tension. It can also present as a cystic with thickened wall, that is, "thick-walled cystic", which can be seen as a unique characteristic of HMH. Binary Logistic regression analysis showed that UES was more prone to spontaneous hemorrhage，and the age was significantly higher than that of HMH（all P＜0.05）. ROC curve showed, that the area under the ROC(AUC) for UES diagnosed by bleeding was 0.861，with a sensitivity 84.2% and specificity 88.0%，and the AUC of the age was 0.931，with a sensitivity of 89.5% and a specificity of 88.0%，best cutoff was 54 months. Conclusion Ultrasound has important clinical value in the differential diagnosis of UES and HMH. Combined with age and bleeding，and reference to the characteristics of echo，the identification of these two diseases can be suggested.