Mild cognitive impairment (MCI) has been described as a transitional state between the cognitive changes of normal aging and dementia, which has a higher risk of conversion to Alzheimer￠s diseases(AD). Therefore, MCI stage may be the most proper time to receive preventive therapy, and it has become the focus of studies. In this paper, we reviewed the recent progress of the neuropsychological testing, biomarker examination, neuroimaging examination, brain electrophysiological examination and treatment in the diagnosis of conversion from mild cognitive impairment to AD.