Ganoderma lucidum polysaccharides were extracted by boiling water from the fruiting bodies of red ganoderma lucidum, then protein was removed by Sevage reagent, with ethanol precipitation, run water dialysis, centrifugation and freeing-drying. Monosaccharides were acetylated and quantified by external standard, and the polysaccharides the amount of total carbohydrates was determined by phenol-sulfuric acid method. The monosaccharide constituents, structure and Mw distribution were analyzed by UV-Vis, IR, GC, GC-MS and HPSEC with ELSD. The results demonstrated that ganoderma lucidum polysaccharides were beige, the yield was about 2%, and the content > or = 43%. IR spectrometry showed that the structure of ganoderma lucidum polysaccharide was pyranoid glucan with beta-glycosidic bond. The quantitative result of external standards indicated that the monosaccharide constituents were mainly composed of glucose, at about 89% percent, and contained a small amount of D-arabinose, D-xylose, D-mannose and D-galactose. It was a homogeneous polysaccharide with the amorphous structure, attributed to biological macromolecules, its Mw distribution was at 80-2000 Kda, and a primary Mw at 2000 Kda.