Abstract: Objective: The aim of our study was to establish the rat models of pulmonary hypertension induced by monocrotaline. Using the micro CT and magnetic resonance (MR) right ventricular function imaging methods, we research the relationship between the evolution of right ventricular structure and function and the evolution of pulmonary artery pressure (PAH). Methods: Ninety-six Sprague-Dawley rats were randomly assigned into two groups: control group (n=48), and four PAH groups (n=48) caused by monocrotaline (MCT). Each group were divided into four groups (1 wk-PAH group, 2 wk-PAH group, 3 wk-PAH group, 4 wk-PAH group). We measured pulmonary artery pressure by right heart catheterization. After injection of MCT, we used the micro CT and MRI to measure the pulmonary artery diameter and the right ventricular function of the rats every week. All measurements of RV structure and function in model group were compared with pulmonary average pressure (PAP) using Pearson's correlation. Results: There were strong correlations between the parameters of RV structure and function in model group with the pulmonary average pressure (r=-0.823 for RV EF, r=0.732 and 0.803 for RV EDV and RV ESV, r=0.694 for the maximum inner diameter ratio of right ventricle to left ventricle). The diameter of main pulmonary artery was not correlated with mean pulmonary artery pressure (r=0.438). After injecting monocrotaline two weeks, the PAP, the maximum inner diameter ratio of right ventricle to left ventricle,, right ventricular eject fraction (RVEF), end-diastolic volume (EDV) and end-systolic volume (ESV) of right ventricle between rats in PAH and the control group showed no significant difference (P > 0.05). But three-four weeks after MCT injection, all these parameters were significant differences in PAH rats than in control group (P < 0.05). Conclusions: As the pulmonary arterial pressure increased in rats, the right ventricular function was gradually impaired. For the monitoring of chronic pulmonary hypertension model in rats, CT and MRI can accurately and rapidly measure the changes of parameters. The PAH can be indicated by observing parameter changes such as the pulmonary artery diameter, the right ventricular volume and cardiac output.