Abstract: On the basis of single factor test, optimization of extraction process of crude Natural Boletus polysaccharides was investigated by orthogonal tests.Then the Natural Boletus polysaccharide was obtained after ethanol-precipitation, deproteinixation and vacuum drying.The results showed that the optimum conditions for the isolation was as follows:temperature was 75℃, time was 2h, material to water ratio was 1∶25, times was 3, polysaccharide yield was 9.13%.The major factors affecting Natural Boletus polysaccharides extraction were material to water ratio and temperature in the first place, and times in the next place.The scavenging ability of ·OH and O-2· of Natural Boletus polysaccharide were assayed by chemiluminescence.There results showed that Natural Boletus polysaccharide had evident abilities of scavenging hydroxyl radicals and superoxide anion radicals.The crude Natural Boletus polysaccharides obtained had strong superoxide anion radicals scavenging effect, with an IC50 of 5.40mg/mL, which was more than 1.18-fold increased after hydroxyl radicals, revealing an IC50 of 6.36mg/mL.