In the study, 20 schizophrenic patients are recruited into the 6-week trial and randomly assigned into the two groups (1 g/d and 2 g/d) with a double-blind manner. Clinical manifestation (Positive and Negative Syndrome Scale; Scale for the Assessment of Negative Symptoms), side effects and quality of life are evaluated every two weeks during the trial. The efficacies of two groups are compared, and the characteristics of better responders are analyzed.