Objective To explore the diameter change of the extrahepatic bile duct before and after laparoscopic cholecystectomy (LC). Methods From Jan. 2006 to Dec. 2007， 113 patients including chronic gallstone cholecystitis （n=55）, inactive cholecystolithiasis （n=46） and gallbladder polyps （n=12） were collected and treated by LC. The diameters of their extrahepatic bile ducts were measured by B ultrasonography before operation， 3 months and 6 months after operation. These data were collected and analyzed retrospectively. Results The diameters of the extrahepatic bile ducts of all patients before LC， 3 months and 6 months after LC were (5±2) mm, (8±2) mm and (6±2) mm respectively. And in chronic gallstone cholecystitis patients they were (5±2) mm, (9±2) mm and (6±2) mm respectively， in inactive gallstone cholelithiasis patients they were (5±2) mm, (8±2) mm and (6±2) mm respectively， and in gallbladder polyps ones they were (5±2) mm, (7±2) mm and (5±2) mm respectively. Conclusion The change of the extrahepatic bile duct diameter after LC is a dynamic process. It is enlarged on the third month after operation than before operation. In the sixth month after operation marked retraction occurs, and compared with before operation, it shows no obvious statistic significance.