This study examined the differences in intestinal health between fast- and slow-growing bullfrogs (Lithobates catesbeianus) fed a soybean meal (SM)-based diet. A total of 108 froglets (26.14 ± 0.21 g) were randomly distributed into three tanks at a density of 36 froglets per tank and fed a SM-based diet for 8 weeks. At the end of the feeding period, four heaviest and four lightest bullfrogs from each tank were captured and considered as fast-growing (FG) and slow-growing (SG) groups. The FG group had significantly higher weight gain than the SG group (p < 0.05). A basic intestinal tissue structure integrity with higher values of jejunal diameter, villus numbers, villus thickness and muscular thickness was observed in the FG group compared with the SG group (p < 0.05). Moreover, lower activity of serum diamine oxidase was detected in FG group than the SG group, which indicated better gut barrier function of froglets in FG group (p < 0.05). However, no significant differences were found in the mRNA expression level of tight junction proteins including occludin and zo-1 in the jejunum, and serum D-lactate concentration between the two groups (p > 0.05). Significantly lower pH values in corpora ventriculi and ileum and higher jejunal protease and amylase activities were found in the FG group than SG group (p < 0.05). Relatively higher expression of anti-inflammatory genes and lower expression of pro-inflammatory genes were found in the FG group; however, the differences were not significant. The abundances of potential probiotics including Akkermansia, Lactobacillus and Prevotellaceae_UCG_001 were higher in the intestinal microflora of FG group compared with the SG group. In conclusion, these findings suggested that higher growth of FG bullfrogs fed the SM-based diet could be attributed to their better intestinal morphological structure and barrier function compared with the SG bullfrogs.