This experiment was conducted to investigate the effects of Astragalus polysaccharide on growth performance and immune functions of broilers. Two hundred and forty one-day-old Arbor Acres broilers were randomly divided into 4 groups with 3 replicates in each group and 20 broilers in each replicate. The basal diets were supplemented with 0, 100, 200 and 400 mg/kg Astragalus polysaccharide, respectively. The experiment lasted for 49 days. Growth performance, immune organ omdocws and immunoglobulin were determined in different periods. The results showed that BW, ADFI, F/G and thymus and bursal of Fabricius indices of broilers fed 200 mg/kg Astragalus polysaccharide diet were significantly affected (P<0.05); adding 100 mg/kg Astragalus polysaccharide to the basal diet significantly affected bursal of Fabricius index (P<0.05) and did not significantly affect the immunoglobulin level in serum of broilers (P>0.05). In conclusion, it can be seen that adding proper amount of Astragalus polysaccharide to the basal diets improved broiler growth performance and enhanced immune organ growth and functions; and 200 mg/kg group was the best among the four groups.［Chinese Journal of Animal Nutrition, 2010，22（4）:1031-1036］