An internal-gearing gear pump having an axial compensation function is disclosed. The internal-gearing gear pump includes a pump body. An end cover and a tail cover are fixedly mounted to two sides ofthe pump body respectively through fastening bolts. A bearing disc is installed inside the pump body and is horizontally placed, and the two ends of the bearing disc are respectively fixed to the endcover and the tail cover. A fixing disc is mounted to the bearing disc through a bearing. A driving wheel is sleeved with the fixing disc. Two sides of the fixing disc are provided with floating sideplates. One side, far from the fixing disc, of each floating side plate is connected to a hydraulic adjusting seat. The outside of the pump body is provided with an adjusting seat through bolts. Twosides of the adjusting seat are provided with air cylinders respectively. Pistons are disposed in the air cylinders, one side of each piston is connected to a pushing bar, and the other end of each pushing bar is provided with a valve plate. The internal-gearing gear pump achieves axial compensation of the floating side plates for the gear pump through hydraulic pressure, and avoids a situation that service lifetime of the floating side plates is shortened due to overlarge hydraulic pressure, so that practicability is improved.