Objective: To study the significance of dementia rating scales in the diagnosis of Alzheimer' s disease (AD).Methods: Probable AD patients(118 cases) diagnosed according to NINCDS-ADRDA criteria and the normal controls(100 cases) were examined with a battery of neuropsychological tests and the dementia severity of AD patients was determined with clinical dementia rating(CDR). Changed neuropsychological characteristics of different AD dementia severities were analyzed. The discriminant analysis and ROC curve analysis were performed to analyze the specificity, the sensitivity, and the general accuracy of various dementia rating scales in the diagnosis of AD, and the area under the ROC curve. Results: The total cognition function in mild (CDR = 1), moderate(CDR = 2) and severe stages(CDR=3) of AD had an obvious trend of continuous decline, with the MMSE values 17.44 ± 2.64, 13.90 ± 4.32, and5.50± 3.90 respectively. The trend of decline of the verbal fluency function in AD was same as that of total cognition function. The visuospatial function was reduced in early stage of AD (CDR = 1 ) and completely lost in moderate and severe AD. Delay memory function began to show decline in the early stage of AD, and the decline turned apparent in moderate and severe AD. Immediate memory function showed unchanged in early stage of AD, while showed decline in moderate AD, and the decline became very quick in severe AD. The impairment of daily living ability and social activity function developed with the severity degree of AD. But the decline of social activity function was very quick in moderate stage of AD. In general, the leading scale to diagnose AD was FOM, followed by RVR, POD, MMSE, BD,ADL and DS. When MMSE was combined with one or more of FOM, RVR, BD, DS, the general accuracy in distinguishing AD from the normal controls was improved. Conclusion: Neuropsychological test is useful in the diagnosis of AD, especially in the early stage. The validity is improved when dementia rating scales are combined correctly.