NOVELTY - Method for synchronously producing biological butanol and nanocellulose from sweet Sorghum, involves carrying out steam explosion on the sweet Sorghum straw residue, carrying out enzymolysis on the steam explosion straw with a enzyme mixture of e.g. cellulase, adding water, homogenizing mixture, adjusting pH, mixing the steam explosion straw solution, water washing solution and sweet Sorghum juice, controlling the sugar content, sterilizing, inoculating a butanol fermentation seed solution, and carrying out butanol fermentation.    USE - The method is useful for synchronously producing biological butanol and nanocellulose from sweet Sorghum (claimed).    ADVANTAGE - The method is continuous, environment-friendly and clean in the production process due to the adoption of the biological method.    DETAILED DESCRIPTION - Method for synchronously producing biological butanol and nanocellulose from sweet Sorghum, involves (a) juicing sweet Sorghum straw to obtain sweet Sorghum straw residue and juice, (b) carrying out steam explosion on the sweet Sorghum straw residue at 1-5 MPa for 0.1 seconds to obtain steam explosion straw and a steam explosion straw solution, (c) carrying out enzymolysis on the steam explosion straw with a enzyme mixture of cellulase, laccase and xylanase at 40-75 degrees C, washing with water, centrifuging, adding a small amount of water to prepare a nanocellulose suspension, and homogenizing mixture at 50-150 MPa, preparing nanocellulose under high-pressure homogenization conditions, (d) adding aqueous solution of cellulose isopropyl alcohol, acetic anhydride and sulfuric acid to the mixture, centrifuging the mixture at 30-60 degrees C for 1-3 hours, and adjusting pH to obtain esterified cellulose acetate, and (e) mixing the steam explosion straw solution, water washing solution and sweet Sorghum juice, controlling the sugar content, adding an inorganic salt, and N source to prepare a butanol fermentation culture medium, sterilizing medium at 121 degrees C for 20 minutes (pH 6.5-7), inoculating a butanol fermentation seed solution, and carrying out butanol fermentation.