In order to study the effects of water soluble alfalfa polysaccharide (WSAP) and astragalus polysaccharide (APS) on proliferation of peripheral blood and splenic lymphocyte in broilers, the proliferation was observed in peripheral blood and splenic lymphocyte treated with two polysaccharides at four concentrations respectively. The T and B lymphocytes proliferation were determined by MTT assay after culture for 48 h. The results showed that WSAP and APS at suitable dosages could significantly stimulate proliferation in peripheral blood and splenic lymphocyte, and WSAP at 20 μg/mL, APS at 100 μg/mL showed to the best advantage. In addition, the effects of APS on proliferation of peripheral blood and splenic lymphocyte in broilers were better than that of WSAP, but the effective additive amount of APS was more than that of WSAP. The proliferation of lymphocyte was likely to be one of mechanisms of WSAP and APS to enhance immunity, and the immunization of different plant polysaccharides was different.［Chinese Journal of Animal Nutrition, 2010，22（3）:670-674］