Glycogen synthase kinase-3 (GSK-3) is an intermediary enzyme in various cellular pathways, and has been implicated in the Pathophysiology and treatment of numerous diseases, including Alzheimer, diabetes, and bipolar disorder. Alzheimer’s disease (AD) is a disorder without a molecular marker in peripheral tissues or a disease modifying treatment. Evidence suggest that the co-relation of diabetes and Alzheimer is clear with the GSK-3. Now day’s researchers taking efforts basically to develop the new GSK-3 inhibitors like lithium. For the development of new GSK-3 inhibitors, we have to understand its molecular mechanism and their involvement in pathological condition. So here we summarize brief introduction and mechanism of GSK-3.