The present invention relates to a rotor assembly of the air tool such as a pneumatic grinder or a pneumatic drill, which operate using the air pressure to the air tool non-contact two-stage rotor assembly for a change in a non-contact in the conventional friction-type, coming from the center of the first rotor by spraying is rotated by the driving force to inject the high-speed air been obtained the rotation is injected into the stator disk is installed around the rotor the flow direction of the parts of the centripetal type rotor disk by air pressure in the high-speed change that, by the high-pressure air a further rotational force obtained obtained as well and to engage to rotate the rotor to the parts and the non-contact state, such as a cylinder case and the cylinder dramatically extend the replacement timing or the tool parts hameuroseo eliminate the wear that occurs in the cylinder or vane life of the conventional product technology, and existing discomfort of the initial eccentric assembly Hameuroseo bring improvements in factor productivity it has excellent effect.