The invention relates to the technical field of rotor pumps of vehicle transmissions, in particular to a rotor pump with an inner rotor floating. The rotor pump with the inner rotor floating comprises a pump case, a pump cover, a rotating shaft, an oil inlet channel, an oil discharging channel, an outer rotor and the inner rotor, wherein the outer rotor and the inner rotor are embedded in a rotor cavity of the pump case, and the inner rotor meshes with the outer rotor. The inner rotor is movably arranged on the rotating shaft and can axially move along the rotating shaft, and therefore reasonable lubricating clearances can be kept between the inner rotor and the working surfaces of the pump case and the pump cover all the time, and the eccentric wear phenomenon is avoided.