Objective To investigate the clinical value of ultrasonography in differentiating joint lesions between suppurative arthritis (SA) and juvenile idiopathic arthritis (JIA).Methods The clinical data of 100 patients with septic arthritis (SA group, 100 joints) and 45 patients with juvenile idiopathic arthritis (JIA group, 105 joints) were retrospectively analyzed. The ultrasound manifestations of the two groups were analyzed and compared.Multivariate binary Logistic regression analysis was used to screen and identify the influencing factors of SA and JIA.Receiver operating characteristic (R0C) curves were plotted to analyze the diagnostic efficacy of each ultrasound manifestation in differentiating SA from JIA alone and in combination.Results Univariate analysis showed that there were statistically significant differences in joint effusion, synovial thickening, synovial thickness and synovial blood flow classification between SA group and JIA group （all P＜0.05）.Multivariate binary Logistic regression analysis showed that articular effusion, synovial thickness and synovial blood flow classification were the influential factors in differentiating SA from JIA （all P＜0.05）.ROC curve analysis showed that the areas under the curve of articular effusion, synovial thickness and synovial blood flow classification were 0.781, 0.935 and 0.910, respectively.The area under the curve of the combined application of the three methods in the identification of SA and JIA was 0.972, with 0.732 as the cut-off value, the sensitivity was 90.5%, and the specificity was 99.0%.Conclusion Ultrasound has a certain clinical value in the differentiation of SA and JIA joint lesions in children, and the combined application of multiple ultrasound manifestations can improve the efficiency of differential diagnosis.