A pneumatic nail gun includes a main body, a cylinder, a muzzle device, a lifting wheel, a piston, a lifting rod, and a nail-striking pin. The piston is movable between a striking position and a non-striking position. The lifting rod is connected to the piston, and has an engaging portion that is engaged with the lifting wheel such that rotation of the lifting wheel drives the piston to the non-striking position, and that is disengaged from the lifting wheel such that the piston is driven by air pressure inside the cylinder to the striking position. The nail-striking pin is connected removably and co-movably to the piston, is spaced apart from the lifting rod, and is adapted for striking a nail when the piston is at the striking position.