In order to alleviate the harm caused by radial force to gear pump, the method of the trapped-oil force offsetting part radial force and the implementation structure of the inner surface of the floating side plate were proposed from the three aspects of the media pressure distribution containing trapped-oil pressure, the calculation of radial force and the structure of the radial force offsetting, and the example operations and analysis were performed. The results show that the essence of the trapped-oil force offset method is to compensate the medium force in the direction of inlet oil through part trapped-oil force at the inlet side, so that the radial force in that direction tends to 0; the top edge oil guide groove of the offset structure is an initial radial force reduction measure, the eight-figure relief groove with offset form can provide a large unloading area and avoid cavitation phenomenon, while the offset circular unloading groove can only provide a small unloading area, thus the trapped-oil force required to offset the radial force is obtained; in the case, the offset rate is up to 46.15%, and the offset values of the eight-figure and the circular unloading groove are 0.32 and 0.56 mm respectively. It is concluded that the trapped-oil offset method is feasible in theory and practice.