NOVELTY - Grade separating of forestry cellulose biomass component comprises crushing agriculture and forestry biomass solid phase material, drying, crushing, cleaning with water and filtering; filtering liquid by alkali, adding oxidant, extracting at middle temperature, secondary pressure filtering to obtain secondary liquid phase and solid phase part, two solid phase part, soaking in alkali solution, extracting and filter pressing; and performing high temperature alkali extracting and concentrating nano-filtration membrane filtrate to obtain precipitate and supernatant fluid.    USE - Method for grade separating of forestry cellulose biomass component for producing fuel alcohol and xylooligosaccharide (claimed).    ADVANTAGE - The method realizes resource utilization, reduces dependence on inlet oil, and reduces pollution to environment.    DETAILED DESCRIPTION - Grade separating of forestry cellulose biomass component comprises crushing agriculture and forestry biomass solid phase material, drying, crushing, cleaning with water and filtering; filtering liquid by alkali, adding oxidant, extracting at middle temperature, secondary pressure filtering to obtain secondary liquid phase and solid phase part, two solid phase part, continuously soaking in alkali solution, extracting at high temperature, and 3 times filter pressing after obtained third solid phase and liquid phase part; and performing high temperature alkali extracting, extracting liquid phase pressure filtrate, and concentrating nano-filtration membrane filtrate to obtain precipitate and supernatant fluid. The precipitate is crude cellulose. The supernatant is adjusted to acidic state. The third solid phase comprises cellulose product. The third liquid phase comprises hemicellulose and lignin mixed solution. The adding final concentration of alcohol is more than 50% in concentrated liquid INDEPENDENT CLAIMS are included for:    (1) preparing fuel alcohol which comprises using obtained cellulose for preparing cellulase or hemicellulase, and fermenting with yeast; and    (2) a method for preparing xylooligosaccharide which comprises adding hemicellulose, crude enzyme cellulose crude product and 5-6 times water at ratio of 5:1-1:1 and mixing at 60 degrees C for 5-16 hours; adding active carbon and decoloring, filtering to remove solid impurities, desalting by ion exchange resin, and performing membrane concentration; and drying to prepare powderlike xylo-oligosaccharide or is oligomer xylose with high concentration through nano-filtration membrane.    The preparation method of immobilized cellulase or hemicellulase includes performing solid fermentation culturing for 3 days and harvesting cellulase or hemicellulase.