Objective To investigate the role of RhoA/Rho-kinase pathway in rat models of left heart disease-associated pulmonary hypertension (PH-LHD).Methods Twenty male SD rats (3-4 week-old, 90-100 g) were randomly divided into two groups (10 rats in each group):the group C (control group) with sham operation, and group H (pulmonary arterial hypertension). The rat model of left heart disease-associated pulmonary hypertension was established by supracoronary aortic banding in the group H, and the sham surgery was applied for the rats in the group C (The titanium clip was fixed at the mediastinal tissue adjacent to the artery rather than the ascending aorta). On day 60 after the operation, the cardiac functions, including right ventricular systolic pressure and pulmonary artery pressure were evaluated. After that, all rats were sacrificed and treated with cardiopulmonary lavage in vivo until the lung became white. Then the left lung tissues were fixed in 4% paraformaldehyde for pathological observation while the right lung tissues were frozen for mRNA detection. Results Compared with the group C, both ventricular systolic pressure and pulmonary artery pressure in the group H were increased significantly (P<0.01). Pathological data demonstrated that the pulmonary artery walls in H group were much thicker than that in the group C. Moreover, vascular wall hypertrophy index in the group H was increased greatly compared with that in the group C (P<0.01). QPCR data showed that mRNA levels of Rho kinase, RhoA and ET-A R in the group H were up-regulated compared with the group C (P<0.01). Conclusions Rat model of left heart disease-associated pulmonary arterial hypertension can be successfully established by supracoronary aortic banding. Rho-kinase-mediated pathway may contribute to the pathogenesis and progress of left heart disease-associated pulmonary arterial hypertension.