Abstract: This study explored active immunization against cholecystokinin in laying hens and the effect on nutrition and physiology. The antibody titers of serum and yolk were examined by ELISA. The performance, nutrient digestibility，the development of pancreas and gallbladder, the activity of trypsin and the level of hormones after immunization were examined. The result showed active immunization against cholecystokinin resulted in development of high antibody titers in serum and yolk,decreased the level of cholecystokinin in blood.After the first booster injection, the antibody titers almost reached peak level.The development of gallbladder and pancreas were not affected by CCK immunization. The specific activity of pancreassecreted enzymes was increased in treated group (CCK). Active immunization had no effect on growth hormone, insulin and leptin in serum. The performance of layers was not affected by CCK immunization. It is concluded that active immunization against cholecystokinin in laying hens has no negative impact on the physiology of hens and results in the production of eggyolk with high content of CCK antibody.