Agomelatine crystal, which is a drug for treating depression, and pharmaceutical compositions thereof are provided. The X-ray powder diffraction spectra of such agomelatine crystal, which is irradiated by Cu-Kα and showed by 2θ(degree), has characteristic diffraction peaks at 12.84, 13.84, 16.14, 18.56, 19.12, 20.86, 21.20, 23.84; its IR absorption pattern has characteristic absorption peaks at about 3234, 3060, 2940, 1638, 1511, 1436, 1249, 1215, 1184, 1032, 908, 828, 755, 588 cm-1, and its DSC endothermic transition temperature is 97.6° C. The use of the agomelatine crystal as an active ingredient in preparing a medicament for the treatment of depression is also provided.