Objective To explore the preventive effects of Radix et Rhizoma Rhei Granule on the occurrence of complicated stress ulcer of stomach (CSUS) in rats after cerebral infarction (CI) and its mechanism. Methods Rat models wi t h CI were established by the occlusion of middle cerebral artery. Preventive tre at ment of CSUS in rats after CI with Radix et Rhizoma Rhei Granule was carried out . Results As compared with the control group (Group A),apoptosis index of gastric mucosal cells was decreased and prolifer ation index increased, 5_HT level and noradrenaline (NE) content in gastric muco sa and plasma were declined, gastric and cholic acid reduced and pH value incre a sed in gastric juice of the treatment group(Group B) (P