Objective: To observe the interventional effects of human amniotic mesenchymal stem cells (hAMSCs) transfected with angiotensin converting enzyme 2 (ACE2) gene on monocrotaline-induced pulmonary arterial hypertension (PAH) in rats． Methods : ① HAMSCs were transfected with lentivirus carrying ACE2 gene，and the expression of ACE2，insulin-like growth factor (IGF-1) ，granulocyte chemoattractant protein-2 ( GCP-2) gene，cell migration and tube formation ability was detected before and after transfection. ② Male，healthy，6-week-old SD rats were randomly divided into normal Control group ( Control group ) ，pulmonary hypertension group ( PAH group) ，human amniotic mesenchymal stem cell treatment group ( hAMSCs group) and ACE2-transfected human amniotic mesenchymal stem cell treatment group ( ACE2-hAMSCs group) ．The mean pulmonary arterial pressure ( mPAP) and right ventricular hypertrophy index (RVHI) were measured 2 weeks after the model was established. The lumen size of pulmonary arterioles and the thickness of vessel wall were observed by HE staining．The mRNA expression levels of GCP-2 ，ACE2 ，α-actin and angiotensin Ⅱ ( Ang Ⅱ ) in lung tissue were determined by QPCR . Results : In vitro cell experiments showed that the cell migration ability and tube formation ability of ACE2- hamscs were higher than those of pure hAMSCs (P＜0. 05) ．Ace2-hamscs up-regulated the mRNA expressions of ACE2 and pro-angiogenic factors IGF-1 and GCP-2 (P＜ 0. 01) ．After 2 weeks of intervention，the mPAP and cardiac RV/ LV + S of the PAH group significantly increased compared with the normal control group (P＜0. 01) ，and the mPAP and cardiac RV/ LV + S of the ACE2-hAMSCs group significantly decreased compared with the PAH and hAMSCs groups (P ＜0. 01 ) ． Compared with PAH group，the mRNA expression level of ACE2 significantly increased in the lung tissue of ACE2-hamscs group． Conclusion ACE2-hAMSCs can significantly reduce the mean pulmonary arterial pressure of monocrotaline (MCT) -induced PAH rat model，and significantly improve pulmonary vascular and right ventricular remodeling．The therapeutic effect of ACE2-hamscs is significant in hAMSCs group. It is considered that ACE2-hAMSCs may not only promote the paracrine effect of hAMSCs，The expression of provascular growth factors GCP2 and IGF-1 can repair the injured pulmonary vascular endothelial cells and reduce the high pressure of pulmonary artery．Moreover，the high expression of ACE2 in hAMSCsis related to the regulation of RAS.