Objective: To compare the effects of internal and external biliary drainage on liver function and regeneration after hepatectomy in rats with biliary tract obstruction. Methods: SD rats were randomly divided into internal drainage group (ID group), external drainage group (ED group) and control group. Rats in both ID and ED group underwent common bile duct (CBD) ligation, and those in control group underwent sham operation. Rats in each group underwent partial (70%) hepatectomy at 72 h after CBD ligation, and those in ID and ED group had simultaneous internal and external biliary drainage, respectively. The serum samples and remnant liver tissue of the rats were harvested on day 0, 1, 2, 3 and 7 after liver resection, and the liver function parameters, and the number of mitotic cells and expression of proliferating cell nuclear antigen (PCNA) in liver tissues were determined, and the ratio of the remnant liver weight to body weight of the rats on day 7 after liver resection was also calculated. Results: Compared with control group, the serum levels of total bilirubin (TIBL) and aspartate aminotransferase (AST) were significantly increased, but albumin (ALB) level was significantly decreased in both ID and ED group at each time point after liver resection (all P<0.05), while the comparison between ID and ED group, with exception of the TIBL level which showed no significant change (all P>0.05), the other two parameters were better in ID group than those in ED group (all P<0.05). Compared with control group, at most of the time periods, the number of mitotic cells in liver tissues of both ID and ED group were significantly decreased (all P<0.05), which in ID group was higher than that in ED group and was significantly different on day 2 and 3 after liver resection (both P<0.05). Both the speed and amplitude of elevation of the increase of PCNA expression level in control group were greater than those in either ID or ED group (all P<0.05), but increase of amplitude and speed of decline of PCNA expression were greater in ID group than those in ED group (all P<0.05). The ratio of the remnant liver weight to body weight at day 7 after liver resection in either ID or ED group was reduced compared with control group (both P<0.05), but it was greater in ID group than that in ED group (P<0.05). Conclusion: After partial hepatectomy in rats with biliary tract obstruction, internal biliary drainage can improve post-hepatectomy liver function and promote regeneration of the residual liver.