Objective: To optimize extracting conditions of polysaccharides from stems of Megacarpaea delavayi

and investigate its anti-oxidation effects. Method: Polysaccharide in stems of M. delavayi was isolated by water extracting-alcohol precipitating method

taking extraction rate of polysaccharides as index

optimal extracting conditions were studied by orthogonal test.The content of polysaccharides was determined.by phenol-sulfuric acid method

moreover

in vitro activities on scavenging free radicals of ·OH and O2-· of the polysaccharide were also observed. Result: Optimal extraction conditions of polysaccharides were as followings:extracted 12 h with 15 times the amount of water at 80 ℃;under these conditions

the average yield of polysaccharides was 1.973% (RSD 1.87%)

the conversion factor between glucose and the polysaccharides was 1.127(n=5)

the content of polysaccharides was 80.17% (RSD 2.13%)in the crude polysaccharides.In addition

the polysaccharides had a certain effect on scavenging free radicals of ·OH and O2-· in vitro and exhibited the dose-effect relation. Conclusion: This optimized technology was stable and feasible with high extraction rate;Polysaccharides in stems of M. delavayi possessed a certain anti-oxidant effect.