〔Abstract〕 Objective To investigate the diagnostic value of linear array endoscopic ultrasonography(EUS) for common bile duct microlithiasis. Methods Data of patients who attended in the hospital and diagnosed as common bile duct microlithiasis and biliary sludge by EUS were selected. A total of 85 patients with magnetic resonance cholangiopancreatography(MRCP) examination and ERCP treatment during hospitalization were enrolled. The results of endoscopic retrograde cholangiopancreatography/endoscopic sphincterotomy(ERCP/EST) were the gold standard for diagnosis. The results of EUS, MRCP, and diagnostic ERCP were compared with the gold standard, and the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the three methods were calculated, respectively. The chi-square test was used for comparison of the above indices. Results Of all 85 patients, 63 had positive EUS results, among whom 5 had false positive results; 22 had negative EUS results, among whom 1 had false negative results. Of all 85 patients, 49 had positive MRCP results, among whom 4 had false positive results; 36 had negative MRCP results, among whom 14 had false negative results. Of all 85 patients, 59 had positive diagnostic ERCP results, among whom 10 had false positive results; 26 had negative diagnostic ERCP results, among whom 10 had false negative results. The sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV), and accuracy of EUS in diagnosing common bile duct microlithiasis were 98.3%, 80.8%, 92.1%, 95.4% and 92.9%, respectively. For MRCP, these values were 76.3%, 84.6%, 91.8%, 61.1% and 78.8%, respectively. For diagnostic ERCP, these values were 83.1%, 61.5%, 83.1%, 61.5% and 76.5%, respectively. The EUS group had a significantly higher accuracy than the MRCP group(χ2=6.986,P<0.05) and diagnostic ERCP group(χ2=8.900,P<0.05). The areas under the ROC curves(AUC) and 95%CIof EUS group, MRCP group and diagnostic ERCP were 0.895(95%CI: 0.802-0.988,P<0.001), 0.804(95%CI: 0.702-0.907,P<0.001) and 0.723(95%CI: 0.598-0.848,P=0.001), respectively. Conclusion EUS has a high diagnostic value in the diagnosis of common bile duct microlithiasis and thus can be used as the preferred examination before therapeutic ERCP.