Objective To explore the efficacy and safety of Polyethylene glycol 3350 plus electrolyte bulk on the schizophrenia patients with constipation induced by clozapine. Methods 150 cases of schizophrenia inpatient and outpatient with constipation induced by clozapine treatment were selected and randoly dirided into the group of polyethylene glycol,lactulose group and non-intervention group with 50 patients in each group and each patient or their families signed the informed consent. The treatment groups took orally with Polyethyle ne glycol 3350 plus electrolyte 13. 7grams,2 times per day and lactulose oral solution 10ml,3 times per day respectively. The non-intervention group was not given a regular basis laxatives, but with cathartic therapy in demand. The period of experiment was 6 weeks including 2 weeks baseline observation period and 4 weeks treatment. Assessment criteria: an overall assessment of all symptoms of patients and each patient's constipation and safety parameters were assessed. Results After treatment for 4 weeks,the total effective rate in three groups was 90.0% ,68.0% ,38.0% (all P ＜0.05). The difference was statistically significant. The normal shape of stool rate was 84.0% ,60.0% ,28.0%. PEG group were better than the other 2 groups at baseline in the first defecation time,the average times of bowel movements per week,theutilization of laxatives during treatment, while symptom score improvement in the stool was significantly better than other groups after treatment. The safety parameters including liver and kidney function, lectrolytes, glucose, ECG, symptoms of schizophrenia such as PANSS score had no obvious change in each group after treatment. Conclusion PEG 3350 plus electrolytes was effective and safe in the treatment of clozapine-indueed constipation in chronic schizophrenia.