Abstract: Objective To explore the effects of Sagittaria sagittifolia polysaccharide on immunologic function in immunocompromised mice.Methods Fifty ICR female mice were randomly divided into five groups(normal control group,model group,high-300 mg/kg·d,midium-200 mg/kg·d,and low-dose100 mg/kg·dpolysaccharide group) by body weight.Sagittaria sagittifolia polysaccharide was administrated intragastrically to the mice by gavage once a day for 28 days.The normal control and model group were treated with distilled water.On the 21st day,the mice in ormal control group was injected with normal saline and the mice in another 4 groups were injected with hydrocortisone of 25 mg/kg for 6 days.The body weight change,organ index(thymus,spleen and liver)and phagocytic function of macrophages of the mice were observed in the study.Results The thymus,spleen,and the liver index were 1.255±0.319,2.380±0.574,and 40.442±1.882 mg/g for the mice in model group and were significantly lower than those of the normal control group(P<0.05 for all).The macrophage phagocytic index(1.794±0.514)of the model group was lower than that of the normal control group(P<0.05).The thymus index was 1.848±0.130,1.835±0.243,and 1.708±0.441 mg/g for the mice in low-,midium- and high-dose group,and the spleen index(3.433±0.250,3.386±0.577,and 2.602±0.609 mg/g) and the liver index(45.478±2.683,45.423±2.109,and 44.934±2.337 mg/g) for the mice in low-,midium- and high dose polysaccharide groups were significantly higher than those of the the model group(P<0.05 for all).The macrophage phagocytic index(2.274±0.590,2.406±0.246,and 2.462±0.444)of the three polysaccharide groups were all higher than those of the model group.Conclusion Sagittaria sagittifolia polysaccharide can enhance nonspecific immunity of mice in a certain extent.