Abstract: OBJECTIVE To characterize the homogeneous polysaccharides from Dendrobium officinale Kimura et Migo and study the hypoglycemic activity of the isolated polysaccharides. METHODS DEAE-cellulose anion-exchange chromatography was used to isolate homogeneous polysaccharides from crude polysaccharides (DOP); Monosaccharide composition was analysed after trimethylsilation; and the chemical structure of isolated polysaccharide was characterized with infrared spectroscopy; The effects of isolated polysaccharides on the levels of fasting blood glucose， plasma insulin， and glycosylated serum protein were estimated using diabetic mice models induced by alloxan. RESULTS Four isolated polysaccharides were isolated from DOP， in which DOP1 had the highest content. DOP1 was composed of arabinose， galactose， glucose and mannose in a molar ratio of 3.5∶1.2∶1.5∶1.0. The infrared spectroscopy of various isolated polysaccharides showed that they all had the obvious characteristic absorption peaks of corresponding monosaccharides. The levels of fasting blood glucose and glycosylated serum protein decreased obviously after a 21 day ig administration in diabetic mice models（P<0.01）， in addition， all the four isolated polysaccharides increased glycosylated serum protein levels in varying degrees after a 21 day dosage (P<0.05~0.01). DOP1 displayed the optimal effects on the improvements of above three biochemistry indexes compared with the other three isolated polysaccharides. CONCLUSION Four isolated polysaccharides from DOP displayed hypoglycemic activity in diabetic mice models induced by alloxan.