To study effect of dietary Inulin on the growth, digestive function, and immunity of juvenile Takifugu obscures, a total of 640 juvenile T. obscures (initial body weight of 6.97 ± 1.32 g) were randomly divided into 4 groups with 4 replicates and data were analyzed by single factor test. Four groups were fed diets with 0% (control group), 0.25%, 0.5% and 1% inulin, respectively. After rearing 8 weeks, the growth, nutritive composition, activities of digestive enzymes, nonspecific immunity enzyme were investigated. The supplementation of Inulin had no significant effect on growth index of juvenile T. obscures (P > 0.05). The crude fat content in the white muscle of 0.25% group (0.87%) was significantly higher than that of 0.5% group (0.82%) and 1% group (0.76%), and the crude protein content in the white muscle of 0.25% group (18.75%) was significantly higher than that of 1% group (18.50%), but showed no significant difference compared with the control group (18.62%) and 0.5% group (18.60%); The activities of pepsin, trypsin, lipase and amylase in intestine were increased with the increase of inulin addition. The activities of glutathione peroxidase and superoxide dismutase in the liver of 0.5% group were significantly higher than in the rest three groups, and the difference was very significant (P < 0.01). The activity of catalase in intestine of 0.5% group was very significantly higher (P < 0.01) than that of 0.25% or 1% group, while the malondialdehyde content was decreased with the increase of inulin addition. Therefore, the added amount of inulin should be 0.5%, a concentration that that cannot promote the growth significantly, but improve the activities of digestive enzymes and nonspecific immunity enzymes of juvenile T. obscures.