Along with the coming of aging society, there are more and more people suffering from cognitive dysfunction or dementia. How to make early diagnosis and intervention for these diseases is an important subject in geriatric study in the new century. In recent years, new and standardized definitions and classifications for the elderly cognitive dysfunction and dementia were achieved, and the specific and practical neuropsychological scales were applied. Many retrospective and prospective epidemiological studies were carried out and then analyzed comparably. Systematic analysis was performed on the risk factors for the elderly cognitive dysfunction and dementia, including mild cognitive impairment. The results provided therapeutic targets for clinical drugs and behavior intervention, and also for research direction on fundamental study and drug development.