Objective: To study the mechanisms of aphasia by observing cerebral blood flow and metabolism changes in language functional areas of the brain using imaging, in order to develop a language rehabilitation plan for aphasia patients. Methods: Fifty-eight patients who suffered from Broca's or Wernicke's aphasia secondly to cerebral infarction were evaluated using the Western aphasia battery and Frenchay dysarthria assessment. CT and MRI were obtained to identify the location of lesions, and the language areas were analysed with magnetic resonance spectroscopy ( MRS) and perfusion-weighted imaging (PWI). The results were compared with those of the contralateral hemisphere. Results: Of the 58 patients, there were 23 Broca's aphasia patients, 29 Wernicke's aphasia patients and six other aphasia types. We excluded five patients accompanied by dysarthria, six patients with other aphasia types and 14 patients with much more disease lesions. Finally, we analysed the remaining 12 Broca's aphasia and 21 Wernicke's aphasia patients by MRS and PWI. MRS shows that the N-acetylaspartate, choline and creatine of the Broca's or Wernicke's area were reduced than those of the contralateral hemisphere, while PWI results show that the damaged Broca's or Wernicke's areas were in a hypoperfusion state. Conclusions: Broca's or Wernicke's area of aphasia patients exhibits hypoperfusion and hypometabolism, indicating that they might be the mechanisms of Broca's or Wernicke's aphasia.