Objective：This study aims to investigate the effects of a novel hybrid compound CDDO -NO from bardoxolone methyl (CDDO-Me)and NO donor isosorbide 5-mononitrate on monocrotaline(MCT)-induced pulmonary arterial hypertension(PAH)in rats. Methods：Male Sprague-Dawley rats were randomly divided into 6 groups：control(Con)group，MCT group，MCT+10 μg/kg CDDO-NO (MCT+10NO)group，MCT+30 μg/kg CDDO-NO(MCT+30NO)group，MCT+7 μg/kg CDDO-Me(MCT+7Me)group and MCT+21 μg/kg CDDO-Me(MCT+21Me)group. PAH in rat was induced by a single dose injection of 60 mg/kg MCT intraperitoneally. The rats in each treatment groups were treated for daily aerosol CDDO -NO or CDDO -Me inhalation for 28 days. Right ventricular systolic pressure (RVSP)by right heart catheter，and right ventricular hypertrophy index(RVHI)as well as RV -to - body weight ratio(RV/BW)were measured. Hematoxylin-eosin(HE)staining was used to detect the pulmonary artery medial thickness(PAMT)and the morphological changes of the right ventricle. And α-smooth muscle actin(α-SMA)immunohistochemistry was used to investigate the muscularization of distal vessels. Masson’s trichrome staining(MTS)was performed to evaluate the fibrosis of arterioles. Results：Right heart catheter and right ventricular remodeling indicators showed that inhalation of either CDDO-NO or CDDO-Me suppressed elevations of RVSP， RVHI and RV/BW induced by MCT in PAH rats. CDDO-NO(30 μg/kg)showed stronger inhibitory effect in RVHI and RV/BW than that of the equal dose of parent compound CDDO-Me(21 μg/kg). Moreover，pathological studies indicated that 30 μg/kg CDDO-NO had better effects in alleviating right ventricular myocardial hypertrophy and PAMT，and reducing the proportion of fully muscularized vessels and the area of collagen deposition than those of CDDO-Me(21 μg/kg). Conclusion：Inhalation of CDDO-NO can ameliorate MCT-induced PAH in rats by inhibiting pulmonary vascular remodeling，and the effect of CDDO-NO is superior to parent compound CDDO-Me. These results suggest that CDDO-NO could be a promising drug for the treatment of PAH.