NOVELTY - Preparing quercetin and rhamnose using Sophora flower bud, comprises extracting crushed Sophora flower bud using saturated clarified lime water, crystallizing and filtering to obtain rutin filter cake, heating rutin filter cake with dilute acid solution, cooling, filtering and drying to obtain quercetin, collecting the filter acid liquid, adding alkaline substance, filtering, fermenting filtrate using dry yeast powder and condensing to obtain rhamnose crude product, dissolving rhamnose crude product in methanol, adding activated carbon and crystallizing to obtain rhamnose.    USE - The method is useful for preparing quercetin and rhamnose using Sophora flower bud (claimed).    ADVANTAGE - The method is economical, has simple process flow, high product yield and low energy consumption, causes less pollution, and produces rhamnose as by-product utilizing the waste liquid generated during quercetin preparation and hence conserves resources.    DETAILED DESCRIPTION - Preparing quercetin and rhamnose using Sophora flower bud, comprises: (a) extracting rutin by crushing Sophora flower bud into 10-20 meshes, adding clean water, mixing, distilling in an extracting tank for 1-2 hours, taking out and drying for 4-8 hours, adding into a percolation tank, discharging colloid using 35-45 degrees C clean water, then extracting using 35-45 degrees C saturated clarified lime water, where the pH value of the effluent is 10-13, adjusting the pH value to 2-6 using inorganic strong acid, crystallizing for more than 4 hours, and filtering to obtain rutin filter cake; (b) adding rutin filter cake obtained in step (a) into an enamel reaction kettle filled with dilute acid solution, heating at a reaction kettle pressure of 0.12-0.15 MPa for 1.5-2 hours, cooling, filtering, washing using purified water to neutral pH, and drying at 75-95 degrees C to obtain quercetin; (c) recycling rhamnose crude product by collecting the filter liquid of step (a), adding alkaline substance to adjust the pH to neutral, filtering, removing precipitate, adding dry yeast powder to the filtrate, fermenting for 24 hours, filtering to remove impurities, adding activated carbon to decolorize, filtering to remove activated carbon, condensing the filtrate, cooling and crystallizing, and filtering to obtain rhamnose crude product; and (d) purifying by dissolving rhamnose crude product in methanol, adding activated carbon to decolorize, filtering to remove the activated carbon, concentrating, cooling and crystallizing, and filtering to obtain rhamnose.