A pneumatic tool includes a rotor rotatably received in a housing, a driving shank coupled to the rotor, for being rotated by the rotor and by a pressurized air and having one end for driving a fastener. A pressure releasing device may release the pressurized air after the fastener has been tightly threaded onto the object to be fastened. A fluid container is rotatably received in the housing and coupled to the rotor, for partially receiving the driving shank. The driving shank has one or more paddles for being frictionally driven by the container and by the fluid. A pole is slidably engaged through the rotor, and actuated to release the pressurized air when the fastener has been tightly threaded onto the object.