Objective:To investigate the cardioprotective effects of Rougui(Cinnamomi Cortex) on diabetic cardiomyopathy in rats. MethodsThe diabetes model in SD rats was established by single intraperitoneal injection of streptozotocin(STZ) at a dose of 85 mg/kg,which then induced myocardial injury. The normal rats were taken as the normal group. The model animals were randomly divided into the model group,captopril group(50 mg/kg) and Rougui group(0.75 g/kg),and were treated with corresponding drugs by intragastric administration. After treatment for 26 days,the animals were anesthetized and the electrocardiogram(ECG) of rats was measured by multichannel physiological signal acquisition and processing system. The left ventricle was separated and weighed,and the left ventricular weight index(LVWI) was calculated. The serum levels of blood glucose(GLU),total cholesterol(TC),triglyceride(TG),high density lipoprotein(HDL) and low density lipoprotein(LDL) were detected by automatic biochemical analyzer. The serum level of brain natriuretic peptide(BNP) was detected by ELISA. The activities of Na,+,K,+,-ATP and Ca,2+,Mg,2+,-ATP enzymes in myocardial tissue were detected by phosphorus quantitation. The contents of phosphocreatin(PCr),adenosine triphosphate(ATP),adenosine monophosphate(ADP) and adenosine monophosphate(AMP) in myocardium were tested by high performance liquid chromatography(HPLC).  Results:Compared with the normal group,the LVWI and the serum levels of GLU,TC,TG,LDL and BNP were significantly increased,and the intervals of QRS,P-R,S-T and Q-T were prolonged in the model group. In addition,the heart rate was slowed down,and the activities of Na,+,K,+,-ATP and Ca,2+,Mg,2+,-ATP enzymes in myocardial tissue and the contents of PCr,ATP,ADP and AMP were significantly decreased. Compared with the model group,the serum levels of TG,TC,LDL and BNP were significantly decreased,the intervals of QRS and P-R were significantly shortened,the Ca,2+,Mg,2+,-ATP enzyme activity and the contents of PCr,ATP and ADP in myocardial tissue were increased significantly in the Rougui group.  Conclusion:Rougui(Cinnamomi Cortex) may improve the myocardial injury in diabetic rats through the effects on energy metabolism of myocardium.