NOVELTY - The preparation method of simvastatin involves adding n-butyllithium and tetrahydrofuran to reaction vessel, adding pyrrolidine to mixture and reacting to prepare solution of lithium pyrrolidine, adding lovastatin and cyclopropylamine to vessel, adding tetrahydrofuran to reaction mixture, adding solution of lithium pyrrolidine to vessel, adding hydrochloric acid solution to organic phase, concentrating and drying to get 2,2-dimethyl-butyric acid 8-(6-cyclopropylcarbamoyl-3,5-dihydroxy-hexyl)-3,7-dimethyl-1,2,3,7,8,8a-hexahydro-naphthalen-1-yl ester (A).    USE - The method is useful for preparing simvastatin (claimed).    ADVANTAGE - The method ensures simple, rapid and efficient preparation of simvastatin under mild reaction conditions with high yield and purity and reduced amount of residual organic solvents and related substance in an environmentally-friendly manner.    DETAILED DESCRIPTION - The preparation method of simvastatin involves: (a) adding n-butyllithium and tetrahydrofuran to a reaction vessel, cooling to -5 degrees C under stirring, adding pyrrolidine to mixture and reacting at -5 degrees C to 0 degrees C for 2 hours to prepare a solution of lithium pyrrolidine; (b) adding lovastatin and cyclopropylamine to a reaction vessel, reacting at 50 degrees C for 5 hours, adding tetrahydrofuran to reaction mixture, cooling to -10 degrees C under stirring, adding solution of lithium pyrrolidine to reaction vessel, reacting at -10 degrees C to -5 degrees C for 1 hour, adding iodomethane to mixture and then reacting at 0 degrees C for 1 hour, leaving, separating organic phase layer, adding hydrochloric acid solution to organic phase layer, leaving, separating organic phase layer and then concentrating under reduced pressure and drying to obtain 2,2-dimethyl-butyric acid 8-(6-cyclopropylcarbamoyl-3,5-dihydroxy-hexyl)-3,7-dimethyl-1,2,3,7,8,8a-hexahydro-naphthalen-1-yl ester (A); (c) dissolving compound (A) in an ionic liquid, adding sodium hydroxide solution to mixture, followed by stirring and heating at 70 degrees C, adding water, reacting at 10-15 degrees C for 3 hours, adjusting pH of the solution to 4 using hydrochloric acid solution, extracting reaction solution using ethyl acetate, leaving, separating ethyl acetate, dripping aqueous ammonia in solution to react at room temperature for 2 hours, leaving, filtering the solution and vacuum-drying filtrate to obtain ammonium 7-(8-(2,2-dimethyl-butyryloxy)-2,6-dimethyl-1,2,6,7,8,8a-hexahydro-naphthalen-1-yl)-3,5-dihydroxy-heptanoate (B); and (d) adding compound (B) and toluene to reaction vessel, refluxing reaction mixture for 3-5 hours, adding activated carbon to mixture and then stirring for 30 minutes and heating, removing activated carbon by filtering, concentrating filtrate, crystallizing concentrate, filtering and cooling. The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, N-ethylpyridinium tetrafluoroborate, 1-butyl-3-methylimidazol-3-ium hexafluorophosphate, 1-hydroxyethyl-2,3-dimethylimidazolium chloride, 1-nitrile propyl-3-methylimidazolium chloride, 1-carboxymethyl-ethyl-3-methylimidazolium chloride, N-methyl-2-pyrrolidone hydrogen sulfate or 1-butyl-3-methylimidazolium hydroxide.