This study examined the effects of preventive atorvastatin (Ator) treatment on vasodilatation of small pulmonary arteries (SPAs) in monocrotaline (MCT)-induced pulmonary hypertensive rats. SD rats were randomly assigned to: normal control (Ctr), pulmonary arterial hypertension (PAH), PAH treated with 5 mg/kg/d Ator (LAtor), or 10 mg/kg/d Ator (HAtor). PAH was induced by MCT injection (40 mg/kg, i.p.). Mean pulmonary artery pressure (mPAP), right ventricular hypertrophy index (RVHI%), endothelium-dependent relaxations (EDdRs), and endothelium-independent relaxations (EDiRs) were determined. Four weeks after MCT injection, mPAP was higher in PAH group compared to that in Ctr group, and this effect was suppressed by Ator treatment (PAH: 32.19 ± 0.91 mm Hg vs. LAtor: 19.13 ± 1.01 mm Hg, HAtor: 17.55 ± 0.20 mm Hg, p < 0.05). Similar trend of changes in RVHI% was found in the same way. EDdRs of SPA rings in PAH group were markedly decreased 2 and 4 weeks after MCT injection, while in Ator treated groups, the impairment can only be detected 4 weeks after MCT injection. There were no differences in EDiRs among all groups 1 week after MCT injection. However, 2 weeks and 4 weeks after MCT injection, EDiRs were significantly impaired, while in HAtor and LAtor groups, EDiR was only impaired 4 weeks but not 2 weeks after MCT injection. Preventive treatment with atorvastatin for 2 weeks ameliorated endothelium-dependent and endothelium-independent vasodilative dysfunction in small pulmonary artery rings of MCT-induced PAH rats. It suggests that MCT-induced damage of endothelial function was progressing, and Ator was only beneficial in the early stage of MCT-induced PAH.