Lung is a major site for the expression of angiotensin-converting enzyme (ACE) and generation of angiotensin Ⅱ (AngⅡ). Studies have showed that the renin-angiotensin system (RAS) involves in the pathogenesis of acute respiratory distress syndrome, pulmonary fibrosis, pulmonary hypertension, asthma, and lung cancer. There are two axes in the RAS, i.e. the ACE/AngⅡ/angiotensin Ⅱ type 1 receptor (AT1R) axis and the ACE2/angiotensin-(1-7) [Ang-(1-7)]/Mas axis. AngⅡ involves in the incidence and development of many pulmonary diseases through its specific receptor AT1R, while Ang-(1-7) counteracts the effect of AngⅡ via specific receptor Mas. This paper reviews the protective effect and possible molecular mechanisms of Ang-(1-7)/Mas during the course of several common pulmonary diseases.