Abstract: Water-soluble crude polysaccharide (wPNP) was extracted from cultured mycelium of the fungus Pholiota nameko by hot water extraction.The extraction rates of polysaccharide were 2.463%.The content of total polysaccharide was determined by the phenol-sulphuric acid method,and the value was 64.98%.The crude polysaccharides were purified by CTAB and Sephadex-150 in sequence,with the obtained one designated as wPNP-a1.The structure of wPNP-a1 was analysed by HPLC,FTIR,GC,NMR,ESEM,and AFM.The results showed that the average molecular weight of wPNP-a1 was 419310 Da.It had the general characteristics of polysaccharide absorption peaks,β-glycoside linkage,and no acetyl.The GC analysis indicated wPNP-a1 was composed of xylose,mannose,galactose,and glucose in molar ratios of 3.91∶2.77∶1.91∶1.The repelling forces between the molecules were stronger than the attractive forces. The wPNP-a1 formed a linear chain on the surface of mica,the width was 23 nm,and the height was 0.7-0.8 nm.