To investigate the effects of dietary bile acids (BA) on growth and metabolism of lipid in grass carp (Ctenopharyngodon idella, C. idella) at high dietary lipid level, a basal diet (50 g kg -1 lipid, 5L group) was supplemented with 20 g kg -1 soybean oil (70 g kg -1 lipid, 7L group); then, 0.06 g/kg BA was added in 7L diet to form the third diet (7L+BA group). The 96 C. idella (69.86 ± 6.24 g) were divided into three groups (duplicate per group) and fed three diets, respectively, for 8 weeks, and then, growth and lipid metabolism were determined. Results showed that growth of fish in 7L+BA group was significantly higher than 5L and 7L groups. The lipid level in whole body, hepatopancreas and muscle of grass carp in 7L+BA group were significantly lower than 7L group.Relative expression of lipid catabolism genes in hepatopancreas and muscle of 7L+BA group was significantly higher than 5L group. The amount of microbiota in intestine of fish in 7L+BA group was significantly higher than the other two groups. The present results indicated that BA in 7L diet improved growth of fish by increasing protein synthesizing, decreasing lipid content in fish body and by regulating amount of microbiota in intestine of fish. K E Y W O R D S adipose triglyceride lipase, fatty acid synthase, growth performance, intestinal microbiota, lipid accumulation, protein deposition How to cite this article: Zhou JS, Chen HJ, Ji H, et al. Effect of dietary bile acids on growth, body composition, lipid metabolism and microbiota in grass carp (Ctenopharyngodon idella). Aquacult Nutr. 2018;24:802-813.