The present invention relates to an agomelatine hydrochloride hydrate of formula I, preparation and use thereof, and to pharmaceutical composition containing it. The agomelatine hydrohalide hydrate obtained through the present method has significant increased solubility than agomelatine, and therefore is more suitable for manufacturing pharmaceutical formulations. In addition, the product enjoys higher stability and purity. Using the present method, product of high purity can be obtained through a simple process, free of any complicated steps. wherein X is Cl.
