NOVELTY - Preparing high purity hesperidin comprises crushing cleaned immature bitter orange, adding n-butyl alcohol aqueous solution, adjusting the pH, heating, soaking and filtering, adding sodium hydroxide-ethanol-aqueous solution into the filter residue, extracting for the first time, heating and extracting, soaking the extract, filtering, adding sodium hydroxide-ethanol-aqueous solution into the filter residue, extracting for the second time, extracting, filtering, combining the two filtrates, placing in refrigerator, filtering the precipitate, crystallizing and drying.    USE - The method is useful for preparing high purity hesperidin (claimed).    ADVANTAGE - The method: consumes less energy; and is environmentally friendly and is suitable for large-scale industrial production and use.    DETAILED DESCRIPTION - Preparing high purity hesperidin comprises (a) crushing cleaned immature bitter orange, adding 40% n-butyl alcohol aqueous solution (5 times the volume), adjusting the pH with to 3-4 with dilute hydrochloric acid, heating to 40-50 degrees C, soaking for 40-60 minutes and filtering, (b) adding sodium hydroxide-ethanol-aqueous solution (5 times the volume) into the filter residue, extracting for the first time, where the concentration of sodium hydroxide and ethanol in the sodium hydroxide-ethanol-aqueous solution is respectively 5% and 70%, heating and extracting at 65-80 degrees C, soaking the extract for 2-3 hours, filtering, adding sodium hydroxide-ethanol-aqueous solution (3 times the volume) into the filter residue, extracting for the second time, where the concentration of sodium hydroxide and ethanol in the sodium hydroxide-ethanol-aqueous solution is respectively 10% and 80%, heating and extracting at 65-80 degrees C, soaking the extract for 2-3 hours, combining the two filtrates, placing in 2-6 degrees C refrigerator for 10 hours, and (c) separating the filtrate by filtering the precipitate, raising the temperature of the filtrate to room temperature, adjusting the pH to 3-5 with an acid solution, crystallizing precipitate to obtain hesperidin crystal when no more precipitate is formed, drying at 80 degrees C to obtain high purity hesperidin when no more not weight is reduced.