The invention provides a method for efficiently preparing cellulose acetate through catalyzing waste biomass by organic solvents. According to the method, dry biomass powder is poured into a reaction vessel; then, a mixed solution of methanoic acid and water is added into the reaction vessel; after the materials are uniformly mixed, hydrochloric acid is added to be used as catalysts; under the condition of 40 to 150 DEG C, oil bath heating and stirring are carried out; pre-treatment liquid is subjected to suction filtration; a hot acid water solution and deionized water are used for sequentially washing solid residue, and the cellulose can be obtained; the dry cellulose powder is poured into another reaction vessel; a mixed solution of acetic acid and acetic anhydride, concentrated sulfuric acid and methylene dichloride are added; oil bath heating is performed under the condition being 50 to 120 DEG C; suction filtration, rotary distillation, rotary distillation product washing, extraction filtering and solid residue vacuum drying are performed; the cellulose acetate is obtained. The method has the advantages that a great amount of cellulose in the waste biomass in the nature can be converted into high-added-value cellulose acetate, and the yield reaches 18.25 percent to 50.16 percent.