In order to study the effects of activity flour of isomalto-oligosaccharides bacterium substance from corn (IBS) with three doses on growth performance and hormone secretion of yellow-feathered broilers, a total of 270 one-day-old yellow-feathered broilers were allocated to 5 groups, including control groups 1, 2 and experimental groups 1, 2, 3. The control group 1 was fed basal diets, control group 2 was fed basal diets added with 4.27 g/kg food-grade isomalto-oligosaccharides, and experimental groups were fed basal diets added with 6, 12, 24 g/kg IBS, respectively. The results showed as follows: 1) compared with control group 1, the mortality in experimental groups 1, 2, 3 was decreased by 33.30%,49.95%,49.95%; at 1 to 52 days of age, the average daily gain in experimental groups 1, 2, 3 was increased by 8.80% (P<0.01), 11.02% (P<0.01), 7.80% (P<0.01), and the feed/gain in experimental groups 1, 2, 3 was decreased by 8.73%(P<0.05), 9.09%(P<0.01), 6.91%(P<0.05); serum T₄ content in experimental group 2 was increased by 2.88% (P<0.05); serum Glu content in experimental group 3 was decreased by 24.75% (P<0.05); in the process of dynamic changes, serum Ins content in experimental group 1 was increased by 40.31% (P<0.05) at 1 h after feeding, and that in experimental group 2 was increased by 40.09% (P<0.05) at 2 h after feeding; in the process of dynamic changes, serum GH content in experimental group 3 was increased by 5.18% (P<0.05) at 1 h after feeding, that in experimental groups 2, 3 was increased by 48.26% (P<0.05), 42.72% (P<0.05) at 2 h after feeding, and overall average of that in experimental groups 2, 3 was increased by 23.65% (P<0.05), 26.29% (P<0.05). 2) Compared with control group 2, the mortality in experimental groups 2, 3 was decreased by 24.97%, 24.97%; the average daily gain of broilers at 1 to 52 days of age in experimental groups 1, 2, 3 was increased by 6.57%(P<0.05), 8.75%(P<0.01), 5.59%(P<0.05); in the process of dynamic changes, serum Ins content in experimental group 2 was increased by 44.55% (P<0.05) at 2 h after feeding; in the process of dynamic changes, serum GH content in experimental groups 2, 3 was increased by 50.24% (P<0.05), 44.63% (P<0.05) at 2 h after feeding, and overall average of that in experimental group 3 was increased by 23.80% (P<0.05). In conclusion, there is a positive effect on growth performance and hormone secretion of yellow-feathered broilers by supplemented with IBS in diets, and the effect of feeding basal diet added with 12 g/kg IBS is the best among three doses in this trial.