Abstract: Dextrin, ginseng pectin, heparin and chondroitin sulfate A at doses of 100 and 200 mg/kg p o, and 100 mg/kg i p were found to have anti-ulcer effects in four experimental ulcers in rats induced by acetic acid, indomethacin, stress-restraint and pyloric ligation. The anti-ulcer action of these polysaccharides were most obvious in the stress-restraint ulcer model (p<0.01), but less obvious in acetic acid induced ulcer. In the indomethacin and pyloric ligation induced ulcers, however, the effects of dextrin and giseng pectin were more potent than chondroitin sulfate A and heparin. Among these polysaccharides, the action of dextrin was the most potent,Dextrin and ginseng pectin were shown to decrease the content of gastric acid and the activity of pepsin, but the actions of heparin and chondroitin sulfate A wereweaker. However, the four polysaccharides showed no direct inhibiting effect on gastric acid and pepsin in vitro.Dextrin and chondroitin sulfate A were found to inhibit the pentagastrin induced secretions of gastric juice, gastric acid and pepsin, but giseng pectin and heparin showed no such actions. However, ginseng pectin and heparin were capable of inhibiting histamine induced secretion of gastric acid. Neverthless the four polysaccharides did not influence the biochemical parameters of pilocarpin induced gastric secretion.