Abstract: The polysaccharide was hot water extracted from Coprinus comatus， and precipitated by ethanol. A polysaccharide named CCP（polysaccharide from Coprinus comatus） was acquired after deproteinixation，and vacuum drying. CCP was a non-starch polysaccharide without any protein， nuclear acid，polyphenol and uronic acid. Its average molecular weight was 947 kD. The unit of the monosaccharide was identified by gas chromatography as glucose，mannose，gala-ctose with a mole ratio of 10.5:1.7:1 respectively after complete hydrolysis by acid. The antioxidant activities were investigated in different assays in vitro， namely scavenging activities of hydroxyl free radicals (·OH) generated by Deoxyribose reaction system and superoxide anion(O 2-·) generated by pyrogallol autoxidation system. Results show that CCP possess antioxidant capacity in vitro.