This experiment was conducted to investigate the modulator effects of astragals polysaccharides (APS) on duodenum mucosal immunity of broilers. Two hundred Arbor Acres broilers were randomly divided into four groups of 50 broilers per group: group Ⅰ was control group, while the other 3 groups were experimental groups which broilers were orally administered with 0.5 mL APS at 3 different concentrations (6, 4, 2 mg/mL) once per day for three days, and broilers in group Ⅰ were oral administratied the same volume of saline. All broilers at 7 days of age were vaccined with combined vaccine against Newcastle disease and infectious bronchitis with 2 times the volume by drop and nasal immunization. Duodenum mucosa was sampled on 8, 15, 22 days of age with ten broilers for detecting contents of immunoglobulin and interleukin-2 (IL-2), and for measurement of the numbers of mucosal immunity-associated cells, respectively. The results showed as follows: contents of immunoglobulin A, immunoglobulin G, immunoglobulin M of duodenum mucosa were significantly higher in broilers at age of 15 days drinking 6 and 4 mg/mL APS than the control (P<0.05). Content of IL-2 in duodenum mucosa and the numbers of intraepithelial lymphocyte, goblet cell and mast cell were significantly higher in broilers at age of 15 and 22 days drinking 6 and 4 mg/mL APS than the control (P<0.05 or P<0.01). It is concluded that oral administration of APS enhances duodenum mucosal immunity of broilers, and the proper concentration of APS was 6 and 4 mg/mL.