Abstract: Extraction of wood hemicelluloses and separation and purification of various polysaccharides from wood hemicelluloses are prerequisites for studying the properties and structures of these polysaccharides. Wood of the fossill tree (Metasequoia glypto-oboides Hu et Cheng), a relic coniferous tree species indigenous to China, was used, Holocellulose was prepared by the method of modifiying the acid sodium chlorite. It was extracted at room temperature by using alkali, filling in nitrogen and sealing the mixture hermetically, then stirring continuously. Afterwards, the selective precipitation of barium hydroxide the fractionation of acid alcohol and the titration of anhydrous alcohol should be carried out to purify it.The sample contained 20% wood hemicelluloses, including 8-9% arabinoxylan and 11-12% glactoglucomannan. Alkali-soluble glucomannan made up 6.26% of the wood and contained glucose and mannose residues in a ratio of 1:1.4-1.6. Water-soluble galactoglucomannan amounted to 4.82% of the wood and contained galactose, glucose and mannose residues in a ratio of 0.3:1:1.8-2.4. The result arrived at following a layer chromatography scanning analysis showed that the above-mentioned polysaccharides were of good homogeneity and high purity.An analysis of the aldononitriles acetates of sugars was also made by gas chromatography. The results of both analysis methods were in fundamental agreement. Therefore. this study suggests that the larger chromatography scanning method can be applied to the quantitative analysis of carbohydrates.