ABSTRACT Objective To explore the ultrasonic features of benign and malignant fat-derived tumors in muscle layer，and to improve the diagnostic accuracy of the disease.Methods The clinical and ultrasonic data of 70 patients with intramuscular fat-derived tumors confirmed by histopathologically were selected.including 36 cases of lipoma （ lipoma group ）and 34 cases of liposarcoma （ liposarcoma group）.The differences of patients with age，sex，location，tumor maximum diameter，boundary，shape，echo level，calcification，anechoic，thin line separations and blood flow grade were analyzed between lipoma group and liposarcoma group.The diagnositic model was established and Logistic regression analysis was conducted.Results There were statistical significance in the tumor maximum diameter，echo level，linear hyperechoic and blood flow grade between the lipoma group and the liposarcoma group （P＜0.05），while in the sex，age，location，boundary，shape，calcification and anechoic between the two groups was no statistically significant （P＞0.05）.Logistic regression analysis showed that the tumor maximum diameter （OR=1.025，P=0.005），echo grade （OR=0.321，P=0.038），and thin line separations（OR=0.048，P=0.001） were independent risk factors of fat-derived tumors，the sensitivity，specificity of the model in the differential diagnosis of the lipoma group and the liposarcoma group were 79%，92%，The area under ROC curve was 0.913.Conclusion The Muscular fat-derived benign and malignant tumors showed some characteristics in clinical and ultrasonic manifestations，which can provide an important reference for clinical diagnosis，differential diagnosis and treatment.