Abstract: OBJECTIVE To explore the optimal dose of monocrotaline(MCT) induced pulmonary arterial hypertension in rats at moderate altitude. METHODS Eighty-five male SD rats were randomly divided into control group, MCT-20 mg·kg^-1 group, MCT-30 mg·kg^-1 group, MCT-40 mg·kg^-1 group, MCT-50 mg·kg^-1 group and MCT-60 mg·kg^-1 group. Except for the control group, all rats received a single subcutaneous injection of MCT, and then were raised in moderate altitude area. Right heart catheterization was used to determine the mean pulmonary artery pressure(mPAP) after 28 d. The right ventricular hypertrophy index was calculated as a parameter of right ventricular hypertrophy. Vascular remodeling was assessed by HE staining. In addition, the general condition, survival rate, body weight, organ coefficient, hematological indexes and success rate of the model in rats were used as auxiliary evaluation indexes. RESULTS Compared with the control group, single subcutaneous injection of MCT-30, 40, 50, 60 mg·kg^-1 could cause increased mPAP, right ventricular hypertrophy and vascular remodeling in rats(P<0.05). The model met the diagnostic criteria for pulmonary arterial hypertension. CONCLUSION MCT-30 mg·kg^-1 is the optimal dose to induce pulmonary arterial hypertension in rats at moderate altitude.