Abstract: In order to study the effect of complexation on the biological activity of polysaccharide, the polysaccharide was extracted from Momordica charantia to prepare the polysaccharide-iron complex.The polysaccharide and its iron complex were characterized by infrared spectroscopy.The effects of the polysaccharide and its iron complex on blood levels of the diabetic mice induced by alloxan were contrasted.Morphology of pancreatic islet cells in paraffin sections of diabetic mice pancreatic tissue were observed by light microscopy.Results showed that the basic framework of the infrared spectrum of the polysaccharide from Momordica charantia did not change much after the complexation of iron ( Ⅲ) , but the local absorption peak moved to the high wave number, and the absorption peak increased at 3407.6 cm^-1. The prepared polysaccharides-iron complex can significantly reduce the blood glucose of the diabetic mice in comparison with those polysaccharides before administration ( p <0.05) .The complex of polysaccharide-iron has better effects on reducing blood glucose than those of polysaccharides alone, and they could protect and restore β cell, promote the regeneration of β particles and mitochondrial, and improve the ability of βcells to release insulin.