Previous studies have suggested that pyroptosis may play an important role in LPS-induced acute lung injury (ALI), but the exact mechanism of pyroptosis induction and the role of Angiotensin-converting enzyme 2 (ACE2)/Ang (1-7)/Mas axis in pyroptosis has not been investigated yet. The present study aimed to establish a mice model of ALI and clarify the involvement of pyroptosis and ACE2/Ang (1-7)/Mas axis. The results showed that LPS induced pyroptosis in lung, demonstrated by increased expression of Gasdermin D (GSDMD), cleaved GSDMD, IL-1β, and Caspase-1. Treatment of Ang (1-7) significantly reduced the severity of ALI and pyroptosis, while AngII significantly exaggerated them. Furthermore, ACE2 activator resorcinolnaphthalein (RES) significantly reduced the severity of ALI and pyroptosis, but ACE2 inhibitor MLN-4760 and Mas inhibitor A779 significantly exaggerated them, suggesting that the ACE2/Ang (1-7)/Mas axis was involved in the pyroptosis in LPS-induced ALI. In addition, Ang (1-7) and RES significantly decreased the levels of NLRP3, which were increased by AngII and A779. NLRP3 knockout significantly reduced the severity of ALI and pyroptosis. In conclusion, pyroptosis played an important role in ALI induced by LPS. The ACE2/Ang (1-7)/Mas axis negatively regulated the pyroptosis and protected mice against LPS-induced ALI through NLRP3 inhibition. The present study expanded our understating of the role of ACE2/Ang (1-7)/Mas axis in ALI by providing a novel explanation that it may regulate the pyroptosis in ALI.