Objectives: This study aimed to evaluate the effect of purgation therapy with Natrii sulfas, an oriental medical therapy for stroke patients with constipation, on physiological indexes and the brain edema of rats. Methods: Brain edema was induced by the middle cerebral artery occlusion (MCAO); Natrii sulfas was administered once after the MCAO. At 3, 6, 15, 24, 48 hours after reperfusion, physiological indexes such as fecal weight, urine volume and water content in stool were assessed, and at 48 hours after reperfusion the edema index was measured. Results: 1. Purgation therapy with Natrii sulfas significantly improved the reduction of fecal weight caused by ischemic insult (P<0.05). 2. Purgation therapy with Natrii sulfas significantly improved the reduction of urine volume caused by ischemic insult (P<0.05). 3. Purgation therapy with Natrii sulfas significantly improved the reduction of water content in stool caused by ischemic insult (P<0.05). 4. Purgation therapy with Natrii sulfas did not improve the neurological symptom caused by ischemic insult. 5. Purgation therapy with Natrii sulfas did not attenuate the total infarct volume caused by ischemic insult. 6. Purgation therapy with Natrii sulfas attenuated the brain edema caused by ischemic insult (P<0.05). Conclusions: These results suggest that purgation therapy with Natrii sulfas improves some important symptoms and has a protective effect on the brain edema caused by ischemic insult.