After high speed centrifugation,enzyme treatment combined with sevag method,crude polysaccharide from gum karaya was prepared by water extraction and ethanol precipitation.Under the activation of BaCl2,selenium-polysaccharides were obtained when hydroxy group of polysaccharide of gum karaya was modified by sodium selenite.The final products were characterized by ultraviolet spectroscopy,infrared spectroscopy and thermogravimetric analysis.The results indicated that the products had a weak absorption peak at 896 cm-1 compared to control group,which is attributed to C—Se=O stretching vibration band.The concentration of selenium-polysaccharide was 1 747.2 mg/kg using ultraviolet spectroscopy.Thermogravimetric analysis showed that the stability of selenium-polysaccharidese decreased a little.