Objective: To analyze the ability of Chinese characters reading and characteristics of alexia among patients with mild, moderate and severe Alzheimer's Disease(AD). Methods: Chinese characters reading test was performed in 20 normal controls(average MMSE total score is 27.7), 20 mild AD(average MMSE is 21.2), 20 moderate AD(average MMSE is 15.2) and 20 severe AD(average MMSE is 6.9). Chinese characters reading test consists of 22 mark-symbol characters, 17 phonetic symbol characters and 17 meaning-symbol characters. Results: No significant difference were found in scores of Chinese characters reading test among normal controls, patients with mild, moderate AD group. Compared with moderate AD, severe AD showed manifest decline for scores of phonetic symbol characters and meaning-symbol characters reading. There wasn't significant different visual paralexia among 4 groups. Surface alexia occurred at early stage of AD and advanced at late stage of AD. These wrong reading were seen frequently in meaning-symbol characters. Deep alexia occurred only at late stage of AD. Compound words phanomenon is the major class of deep alexia. Conclusion: Ability of Chinese characters reading was helpful to estimate premorbid intelligence of the patients with dementia. There are different classes of alexia between Chinese and western languages.