NOVELTY - Deoxynojirimycin alkaloid is extracted by crushing mulberry branch, mulberry tree leaf, and/or mulberry root raw material, extracting, heating total extract to 85-100 degrees C, concentrating, standing concentrated liquid for 12 hours, and filtering; passing filtered liquid through adsorption resin, washing resin with deionized water, eluting with 65-95% ethyl alcohol, collecting elution liquid, and concentrating aqueous phase; adding aqueous phase with ethyl acetate and extracting; dissolving dried extract with anhydrous ethyl alcohol and crystallizing to obtain deoxynojirimycin crystal.    USE - Method for extraction of deoxynojirimycin alkaloid (claimed).    ADVANTAGE - The method has simple and short process, low cost, and high yield.    DETAILED DESCRIPTION - Extraction of deoxynojirimycin alkaloid comprises:    (A) crushing mulberry branch, mulberry tree leaf, and/or mulberry root raw material, extracting the raw material for 4 times, and combining extraction liquids to obtain total extraction liquid;    (B) heating total extraction liquid to 85-100 degrees C, vacuum distilling and concentrating, standing concentrated liquid for 12 hours, allowing impurities in the concentrated liquid to precipitate, and filtering and separating precipitate to obtain filter liquid;    (C) passing filtered liquid through adsorption resin, washing resin with deionized water till effluent liquid is colorless, then eluting with 65-95% ethyl alcohol, collecting elution liquid, recovering alcohol solvent, and concentrating aqueous phase;    (D) adding aqueous phase concentrated liquid with 5 wt.% activated coal powder at 60-70 degrees C, stirring for 30 minutes, filtering and removing activated coal powder to obtain filtered liquid;    (E) adding filtered liquid with 10 times ethyl acetate, extracting twice for 0.5 hour each time, combining extraction liquid, recovering solvent, concentrating extraction liquid, and vacuum drying at 80 degrees C to obtain extract;    (F) crushing extract to 100 meshes and sieving to obtain extract containing 65% deoxynojirimycin; and    (G) dissolving extract with anhydrous ethyl alcohol and crystallizing to obtain deoxynojirimycin crystal.