The recent identification of angiotensin-converting enzyme 2 (ACE2) and Mas receptor opened new recognition of renin-angiotensin system (RAS). ACE2, a homologue of angiotensin-converting enzyme (ACE) generates angiotensin 1-7 directly through cleaving angiotensin II, or indirectly through angiotensin I in the body. Ang 1-7 exhibits vasodilatory and antiproliferative effects, and these effects were mainly mediated by Mas receptor. So ACE2-angiotensin1-7- Mas axis was considered a negative regulation in renin angiotensin system (RAS), and its significance has been implicated into hypertension and other cardiovascular diseases. The identification of the axis opens a new potential venue for further study and understanding of RAS.