The study is a prospective cohort study that included 400 subjects with MCI enrolled in at Huashan Hospital in Shanghai, China and a followed-up once annually for three years. The objectives are to identify individuals with MCI who convert to AD and to explore factors associated with the conversion. The observation time point is every 12 months and phone interview on 6th, 18th month. The primary endpoint was the time from diagnosis to the conversion from MCI to Probable AD Dementia. The secondary endpoints are the time to conversion from MCI to Possible AD Dementia or Probable AD Dementia, time to Conversion from MCI to All-cause Dementia, Overall survival, Changes in Neuropsychological examinations and Changes in MRI from baseline to the end of follow-up. The planned research duration was from Jan 2012 to Dec 2016.