A pneumatic engine, comprising: a rotating outer ring (1), an intermediate shaft (2), a direct drive power core (3), and left and right baffles (4) and (5) where the rotating outer ring (1), the direct drive power core (3), and the left and right baffles (4) and (5) are coaxially provided on the intermediate shaft (2), the rotating outer ring (1) is integrally connected to the left and right baffles (4) and (5) to engage with the intermediate shaft (2) via a bearing, and a closed space is formed, the intermediate shaft (2) is provided with a master air inlet (21) and a master air outlet (22), the direct drive power core (3) is provided with a logarithmic spiral line runner, multiple drive grooves (11) are provided on an inner ring surface of the rotating outer ring (1). The pneumatic engine has a simple structure, high transmission efficiency and strong endurance.