Objective:To examine the discriminatory potential of the Cognitive-12 for moderate and severe Alzheimer＇s disease(AD). Methods:Patients with AD(61 moderate AD and 55 severe AD) were recruited. The COG-12,AD8,MMSE and CDR were tested by all AD subjects. Results:The total scores of COG-12,AD8,MMSE and CDR differed significantly between moderate and severe AD groups with higher scores in severe AD group. The results of multiple linear regression analysis showed insignificant influence of age or educational level on the COG-12 total score. COG-12 could classify moderate and severe AD efficiently with sensitivity of 90.9% and specificity of 70.5%. Conclusion:COG-12 is useful for staging of moderate and severe AD.