<p>A pneumatic engine(1) comprises: a compressed air tank(2) including an inlet port(21) and an outlet port(22); a power module connected with the compressed air tank(2) including at least one cylinder(112) with a piston(113), an inlet valve(321) and an exhaust valve(322); a solenoid valve(34) connected with the inlet valve(321) and the exhaust valve(322) controlling their exhausting frequency; and an ignition system(37) connected with the signal of the solenoid valve(34). The solenoid valve (34) controls the exhausting frequency so that the compressed air in the air tank is exhausted from the outlet port (22) and pushes the piston (113) through the inlet valve (321), and then is exhausted from the exhaust valve (322) into the compressed air tank through the inlet port (21).</p>
