Abstract: The experiment was conducted to study the effects of Gentiana Polysaccharides on immune function in chicken.120 Avian broilers were randomly divided into 4groups and fed by oral.A series of tests were carried out such as thymus index, spleen index and histopathology on 7th,14 th,28 th and 42 thafter vaccination.The results indicated that at the dosage of 50 and 100mg/kg, GP could increase thymus index ,spleen index and enhance development of immune organs.The study proved that GP can promote immune function of chicken.