The present invention discloses a crystalline form of S-zopiclone (Formula I) having a powder X-Ray diffraction spectrum excited by Cu-Ka radiation with characteristic peaks expressed in terms of 2θ at about 11.08°, about 12.38°, about 15.86°, about 17.88°, about 19. 98° and about 20.58° a DSC thermogram with a peak at about 207.7° C. and an infrared absorption spectrum (IR) with characteristic peaks at about 3078 cm−1, about 2942˜2838 cm−1, about 2790 cm−1, about 1716 cm−1, about 1463 cm−1, about 1372 cm−1 and about 757 cm−1. The present invention also discloses a method for preparing the crystalline form of eszopiclone, its pharmaceutical composition and its use in preparing a medicament for treating sleep disorders.
