Abstract: Objective To investigate the value of endoscopic ultrasonography( EUS) in the diagnosis of common bile duct stones. Methods A total of 98 patients who attended The First Affiliated Hospital of Anhui Medical University from June 2017 to May 2019 and were suspected of common bile duct stones were enrolled. All patients underwent EUS and magnetic resonance cholangiopancreatography( MRCP) during hospitalization. The results of open/laparoscopic common bile duct exploration and endoscopic retrograde cholangiopancreatography/endoscopic sphincterotomy were the gold standard for diagnosis. The results of EUS alone,MRCP alone,and EUS combined with MRCP( positive results of EUS or MRCP were considered positive,and negative results of both EUS and MRCP were considered negative) 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. The chi-square test was used for comparison of the above indices. Results Of all 98 patients,92 had positive EUS results,among whom 5 had false positive results; 6 had negative EUS results,among whom 3 had false negative results. Of all 98 patients,69 had positive MRCP results,among whom 2 had false positive results; 29 had negative MRCP results,among whom 23 had false negative results. Of all 98 patients,94 had positive MRCP/EUS results,among whom 5 had false positive results; 4 had negative MRCP/EUS results,among whom 1 had false negative results. The EUS group had a significantly higher sensitivity than the MRCP group( 96. 67%vs 74. 44%,χ2= 17. 982,P < 0. 05),while there was no significant difference in sensitivity between the EUS group and the combined group( 96. 67% vs 98. 89%,χ2= 1. 023,P = 0. 312). There were 52 patients who were suspected of biliary microlithiasis( ≤0. 5 cm),among whom 51 had positive EUS results,including 3 patients with false positive results; 1 had false negative EUS results; among these 52 patients,36 had positive MRCP results,including 1 patient with false positive results; 16 had negative MRCP results,including 14 patients with false negative results; all 52 patients had positive results of EUS combined with MRCP,among whom 3 had false positive results. The EUS group had a significantly higher diagnostic sensitivity than the MRCP group( 97. 96% vs 71. 43%,χ2= 13. 303,P < 0. 05),while there was no significant difference between the EUS group and the combined group( 97. 96% vs 100%,P = 1. 0). Conclusion EUS has great advantages in the diagnosis of common bile duct stones,especially biliary microlithiasis. EUS has a high diagnostic value and can thus be used as the preferred examination before invasive operation.