OBJECTIVE To investigate the effect of Rhodiola Sacra on left ventricular remodeling in spontaneously hypertensive rats (SHRs). METHODS 30 male SHRs were randomly allocated into a treatment and a control group, which were intragastric administered with Rhodiola Sacra 500 mg/(kg x d) and water respectively. Tail systolic blood pressure (SBP) was monitored every two weeks. After 8 weeks, the body mass (BM) and left ventricle mass (LVM) of the rats were measured for computing the left ventricle mass index (LVMI). Plasma and myocardial homogenate angiotensin II (Ang II), aldosterone (ALD) and the protein of myocardial homogenate were detected respectively by radioimmunoassay, and then the quantity of Ang II and ALD per gram protein was calculated. Myocardial specimen slides were stained with method of Masson staining, and myocardial collagen volume fraction (CVF) was calculated by a Computer Image System. Protein expression of Ang II type 1 receptor (AT1) in left ventricular myocardium were detected by immunohistochemistry technique, and calculated by a Computer Image System. RESULTS Compared with the control group, there was a obvious decrease in SBP (P < 0.05), LVMI (mg/g, 2.84 +/- 0.13 vs. 2.97 +/- 0.12, P = 0.044), myocardial CVF (%, 4.41 +/- 0.53 vs. 4.89 +/- 0.53, P = 0.021), plasma Ang II (ng/L, 77.61 +/- 14.12 vs. 92.59 +/- 16.64, P = 0.042), plasma ALD (ng/L, 73.52 +/- 18.61 vs. 90.11 +/- 19.67, P = 0.005), myocardial Ang II (ng/g x protein, 40.03 +/- 5.36 vs. 46.02 +/- 6.78, P = 0.005) or myocardial ALD (ng/g x protein, 37.61 +/- 6.25 vs. 43.70 +/- 5.09, P = 0.049), whereas no significant difference was observed in the protein expression of AT1 in left ventricular myocytes between the two groups. CONCLUSIONS Rhodiola Sacra may prevent left ventricular remodeling in SHRs, which is probably attributed to blood pressure lowering and inhibition of RAS, especially myocardial RAS.