Objective:To identify the sources of repetition difficulties of aphasic patients by Psycholinguistic Assessment in Chinese Aphasia. Method: A conduction aphasic patient and a mixed aphasic patient were tested with Psycholinguistic Assessment in Chinese Aphasia. Result: The case 1 with condution aphasia showed normal auditory and reading word-picture matching, indicating his normal semantic system. The tests on consonant-pair, vowel-pair, intonation-pair, word-pair discrimination were normal, indicating his intact input phonological processing. His non-word repetition, high-image word repetition and word-repetition with seeing-picture were impaired. Single syllabe word-repetition was better than three syllables word-repetition, showing word length effect. Single syllable non -word repetition was much worse than single syllable word repetition, suggesting unstable phonological representations of verbal materials in the output buffer. The case 2 with mixed aphasia showed his auditory and reading word -picture matching were impaired, and consonant -pair, vowel -pair, intonation -pair, word -pair discrimination were impaired. Non-word and word- repetition were impaired, and did not show word length effect. Conclusion: The repetition difficulty of the conduction aphasia is caused by difficulty in maintaining stable phonological representations of verbal materials in the output buffer. The repetition difficulty of the mixed aphasia is greatly related with impaired phonological discrimination.