Abstract: The biological activity of galactooligosaccharides (GOS) produced continuously by immobilized galactosidase was studied. It was verified by animal examination and bifidobacteria culture in vitro that GOS had the ability of promoting the growth of bifidobacteria efficiently and specifically, improving the intestinal microflora in albino rats, reducing serum cholesterol concentration, lowering cecal pH and increasing the calcium absorption and feed efficiency.