In order to achieve gear longitudinal modification and improve gear grinding efficiency, a novel gear grinding methodology is proposed, and the method of accurate control of longitudinal modification values is given. The core principle is that the grinding disc is installed obliquely to generated grinding teeth, and cubic boron nitride (CBN) is sintered on the grinding disc. Firstly, the principle of a novel gear grinding methodology is expounded. Secondly, based on this methodology, the control and adjustment model of longitudinal modification values is established, and it is concluded that the longitudinal modification values can be accurately controlled by the installation angle of the grinding disc. Finally, the effectiveness of this grinding methodology in achieving the whole teeth width grinding of gears and longitudinal modification, as well as improving gear grinding efficiency, is confirmed through VERICUT machining simulation; then, the analysis of tooth contact in the grinding gear pair revealed that longitudinal modification can effectively reduce the edge contacts, which can make the tooth surface load evenly distributed in tooth width direction.