Abstract:The aim of this study was to study the difference of polysaccharide content in fruiting body of Cordyceps militaris from different sources and the difference of antioxidant activity of each component of graded alcohol precipitation.Cordyceps militaris polysaccharides（CMP）and Cordyceps oryzae polysaccharide（COP）were obtained by hot water extraction and fractionated alcohol precipitation.1，1-diphenyl-2-picrylhydrazyl（DPPH）radical scavenging rate，·OH scavenging rate and ferric reducing antioxidant power（FRAP）were used to evaluate the antioxidant activity of the two polysaccharides in vitro.The oxidative damage model of PC12 cells induced by H2O2was established，and the protective effects of two kinds of Cordyceps polysaccharides on oxidative damaged PC12 cells were compared.In the Cordyceps polysaccharide precipitated by different ethanol concentration，the extraction rate and content of COP were higher than those of CMP.The scavenging rates of DPPH free radicals and·OH of COP were 66.43% and 69.22%，respectively，and the reduction rates of CMP were 73.69% and 73.50%.FRAP showed that CMP had strong antioxidant capacity.The results of cell experiments showed that the cell survival rate of oxidative damaged PC12 cells increased in varying degrees after treatment with two kinds of polysaccharides in a concentration-dependent manner.The highest cell survival rate was 90.45% in CMP group and 82.62% in COP group.The extraction rate and content of polysaccharides of Cordyceps militaris with silkworm pupa as medium were lower than those of Cordyceps oryzae with rice as medium，but its polysaccharides were better than COP in scavenging free radicals and protecting PC12 cells.