Objective:To explore the involvement of signal transducer and activator of transcription 3(STAT3) in angiotensin Ⅱ(AngⅡ) induced vascular endothelial growth factor(VEGF) expression and the role of angiotensin converting enzyme(ACE) in regulating STAT3 phosphorylation in mesenchymal stem cells(MSCs). Methods:STAT3 phosphorylation under AngⅡ stimulation was analyzed by Western blot analysis. siRNA targeting STAT3 (STAT3 siRNA) was used to inhibit STAT3,and its effect on VEGF production was examined by measuring VEGF protein level in conditioned media and VEGF mRNA expression in MSCs with ELISA and real-time PCR,respectively. Besides,captopril was used to specifically inhibit ACE,and its effect on STAT3 phosphorylation was analyzed by Western blot. Results:① AngⅡ stimulation significantly increased STAT3 phosphorylation level;② Pretreatment with STAT3 siRNA markedly abolished the AngⅡ-induced increase of VEGF mRNA expression and protein synthesis;③ Captopril significantly inhibited the AngⅡ-induced STAT3 phosphorylation. Conclusion:STAT3 is involved in the AngⅡ-stimulated VEGF expression,and the AngⅡ-induced STAT3 phosphorylation is ACE dependent in MSCs.