The present invention disclosed a crystalline of S-zopiclone having a powderX-Ray diffraction spectrum using Cu-Ka radiation with characteristic peaksexpressed in terms of 2.theta. at about 11.08°, about 12.38°,about 15.86°, about17.88°, about 19.98° and about 20.58°； a DSC thermogramwith a peak at about207.7°C and an infrared absorption spectrum (IR) with characteristicpeaks atabout 3078cm -1, about 2942-2838cm -1, about 2790cm -1, about 1716cm -1, about1463cm -1, about 1372cm -1 and about 757cm -1. The present invention alsodisclosed a method for preparing the crystalline of eszopiclone, itspharmaceuticalcomposition and its use in preparing a medicament for treating sleep disorder.
