The invention discloses a method for preparing microcrystalline cellulose taking xylose residue as a raw material and belongs to the technical field of chemical fibers. According to the method, scraps generated in xylose production, namely, xylose residue, is taken as the raw material, and hydroxyl radical reactive oxygen is taken as a chemical agent and is utilized for dissolving the xylose residue to prepare the microcrystalline cellulose through catalysis, oxidization and bleaching technologies. The method comprises the following technical steps of: (1) preparation of the chemical agent, (2) dilution and impurity removal, (3) separation and dehydration, (4) vacuum drying, (5) catalytic oxidization, and (6) washing, drying and smashing: drying and smashing collected cellulose samples, so as to obtain a microcrystalline cellulose product for synthetic leather. According to the method disclosed by the invention, the problems of low resource utilization rate, serious environment pollution and the like in the corncob industries at present are solved, the production cost is reduced greatly, the harmonious development of resources and environments is promoted, and therefore, the method has important popularization and application values as well as a wide market prospect.