Abstract: Objective To explore the expression changes and clinical value of high mobility group box1 Protein (HMGB1) in hypertrophic myocardium of hypertensive rats. Methods Pressure-overload models were built in healthy adult male wistar rats (8-10weeks old) by partial abdominal aorta ligature method. Wistar rats were divided randomly into 2 groups: the myocardial hypertrophic group and control group. After 4 weeks, they were killed. The in vitro cardiac size was observed and the ventricular weight/body weight ratio (mg/g) was calculated. Cardiac specimens were obtained. Westem Blot was performed to detect HMGB1 protein in myoeardium. Results Comparing with control group, the expression of HMGB1 Protein were increased significantly in myocardial hypertrophic group (P<0.05). Conclusion The pressure-overload may cause the expression of high mobility group box1 protein increase and activation. HMGB1 protein may be involved in the occurrence and development process of myocardial hypertrophy.