NOVELTY - Nalmefene hydrochloride is prepared by adding tetrahydrofuran, methyltriphenylphosphine bromide, and potassium tert.-butoxide in reaction container, keeping temperature, stirring, adding naltrexone, keeping reaction temperature, stirring, keeping temperature, adding purified water, stirring, decompression filtering, washing filter cake with tetrahydrofuran, re-filtering, decompression distilling filtered liquid, adding to trichloromethane, stirring, keeping temperature, adding concentrated hydrochloric acid, stirring, pressure-reduced filtering, washing with chloroform, and vacuum drying.    USE - Preparation of nalmefene hydrochloride.    ADVANTAGE - The preparation reduces use of inorganic salt and waste discharge pollution, enhances product safety, saves material, avoids adding excess organic solvent, has short production time, is reliable, and obtains product which achieves required quality standard.    DETAILED DESCRIPTION - Nalmefene hydrochloride is prepared by sequentially adding 153 ml tetrahydrofuran, 11 g triphenyl phosphine bromide, and 34.5 g potassium tert.-butoxide in reaction container under stirring condition, keeping temperature at 45 plus minus 5 degrees C, continuously stirring for 35 plus minus 5 minutes, dropwise adding 17 g naltrexone in which naltrexone is dissolved in tetrahydrofuran solution, keeping reaction temperature at 40 plus minus 5 degrees C, continuously stirring for 9 plus minus 1 hours, keeping temperature at 45 plus minus 5 degrees C, dropwise adding 8.5 ml purified water, continuously stirring for 10 minutes to obtain reaction liquid, decompression filtering, washing filter cake with tetrahydrofuran, re-filtering, discarding filter cake, decompression distilling filtered liquid twice to obtain red-brown solid shaped substance, adding to trichloromethane, stirring to fully dissolve, keeping temperature at 20 plus minus 5 degrees C, dropwise adding concentrated hydrochloric acid to adjust pH to 3, continuously stirring for 4 plus minus 0.5 hours, pressure-reduced filtering to obtain filter cake, washing with chloroform, vacuum drying in tank to obtain white solid, adding to acetone and hydrogen chloride ethyl ether solution, controlling temperature at 45 plus minus degrees C, continuously stirring for 2 plus minus 0.5 hours, fully dissolving, pressure-reduced filtering to obtain filter cake, washing with acetone, re-filtering, vacuum drying filter cake in tank to obtain nalmefene hydrochloride crude product, mixing 23 g crude product, 46.8 ml purified water, and 0.234 g coal, heating to 70 plus minus 5 degrees C to dissolve, pressure-reduced filtering, re-filtering filtered liquid, mixing filtered liquid with distilled water, cooling to separate out crystals, pressure-reduced filtering to obtain filter cake, washing with acetone and anhydrous diethyl ether, and drying.