The present invention relates to the novel crystalline Fonn-II of Esomeprazole magnesium trihydrate salt and the process for the preparation thereof. Esomeprazole magnesium trihydrate salt is chemically known as (-) 5-methoxy-2- [[(4-methoxy-3, 5- dimethyl-2-pyridinyl)-methyl] sulphinyl]-IH-benzimidazole magnesium trihydrate, which is represented by the Fonnula (1). The process for the preparation of novel crystalline Fonn-II of Esomeprazole magnesium trihydrate salt comprises the reaction of Esomeprazole with magnesium metal in a mixture of methanol and dichloromethane to result the magnesium salt of Esomeprazole. The resulted salt is successively washed with acetone, recrystallized in methanol and isolated the solid using mixture of water and acetone to afford the novel crystalline Form-II of Esomeprazole magnesium trihydrate salt. The process of the present invention is simple, eco-friendly and cost effective and commercially viable over prior art process.