The six polysaccharide fractions were prepared by chromatographic procedure from the hot water extractsof the aboveground parts of Astragalus membranaceus. These six polysaccharides from aboveground parts of Astragalusmembranaceus Bunge were tested for gut-mucosal immune activity and acute toxicity. In a view of molecular weight, the sixfractions were estimated to be 75000, 88000, 129000 and 345000 Da, respectively. Component sugar analysis indicated thatthese fractions were mainly consisted of galactose (46.3~11.8%) and arabinose (35.4~9.9%) in addition to glucose,rhamnose, fucose, arabinose, xylose, mannose, glucuronic acid and galacturonic acid. Among the six major purifiedpolysaccharides, AMA-1-b-PS2 showed highest bone merrow cell proliferation and lymphocyte of Peyer's patch stimulatingactivity. It may be concluded that intestinal immune system modulating activity of aboveground parts from Astragalusmembranaceus Bunge is caused by polysaccharides having a polygalacturonan moiety with neutral sugars such as arabinoseand galactose. In single oral dose toxicity study, no differences were observed between control and treated groups in clinicalsigns. The results indicated that lethal dose 50 (LD50) of water extracts from Astragalus membranaceus-aboveground partswas found to be higher than 5000㎎/㎏/day in this experiment. From the above results, we may suggest that Astragalusmembranaceus-aboveground parts might have useful as a safe material for functional food and pharmaceutics.