Objective:To investigate the effects of Metarhiziun taii polysaccharide on the immunity activity of the diabetic mellitus model mouse.Methods:To build stables type Ⅰ diabetic model mouse by intraperitoneal injecting small dose streptozotocin ( STZ) continuously.Then observeing weight changes,detecting empty stomach serum glucose,immune organ index( include spleen and thymus),peritoneal macrophage phagocyte ability,spleen lymphocyte multiplication and immunoglobulin IgG′s and complement C3,C4 content in blood serum of the diabetic rats.Results:The weight of model mouse had been improved by Metarhiziun taii polysaccharide, serum glucose had been improved degrade of the ability of model mouse.T,B lymphocyte proliferation had been increased obviously by middle and high dose polysaccharid,spleen index,IgG′s and C3,C4 content in blood serum of the diabetic rats could be improved by high dose distinctively.Thymus index and the capacity of peritoneal macrophage phagocyte would enhanced by middle and high dose polysaccharide inject.Conclusion:The immune function and serum glucose of typeⅠdiabetic mode rats could be improved by intra-gastriced Metarhiziun taii polysaccharide.