This experiment was carried out to elucidate the sugar composition of polysaccharides and the structural features of water-soluble polysaccharides(WSP) isolated from Korean oak mistletoe, Loranthus yadoriki Sieb. The 48-hours ball-milled meals of extractive-free dried mistletoe sawdusts were extracted with distilled water for $24hrs{ imes}2$ at room temperature. The extracts poured into 95% ethyl alcohol to precipitate. The separated precipitate of WSP, in form of yellowish white powder by lyophilization, was fractionated into four subfractions of WSP-1, WSP-2, WSP-3 and WSP-4 by anion exchange chromatography on DEAE-cellulose column. The sugar composition of WSPs was analyzed by GLC in form of their glycitol acetates, and the structure of polysaccharides in Fractions WSP-1 and WSP-2 was determined by FT-IR and GC-MS after methylation through and acetylation. The sugars of WSPs from Korean oak mistletoe, Loranthus yadoriki, are majorly arabinose and galactose in stem, galactose in leaves very high in content and showed difference in composition and monomeric units between stems and leaves. D-galactose, D-glucose and L-arabinose are the simple sugars consisting of polysaccharides in WSP-1. ($1{ ightarrow}3$)-Linked galactan is the bakcbone with side chain of ($1{ ightarrow}5$)- -L-arabinofuranosyl residues and ($1{ ightarrow}6$)- -D-galactopyranosyl residues, and ($1{ ightarrow}4$)-linked glucan also presents. ($1{ ightarrow}4$)-Linked rhamnogalacturonan and ($1{ ightarrow}4$)- and ($1{ ightarrow}3$)-linked galactan present in WSP-2.