The utility model discloses a gear of a speed change device and a novel wedge-shaped structure of teeth of the gear. The novel wedge-shaped structure comprises a top face, a bottom face and a Bezier curve face. Extracting involutes and addendum circles of gear teeth, and forming a closed curve with a section of circular arc and two straight lines to form a contour curve of the bottom surface; thetop surface is a rounded rectangle and has a certain height from the bottom surface; bessel high-order curve transition is adopted between the top face and the bottom face, the same corresponding point between the top face and the bottom face starts from the same patrolling direction, Bessel high-order curve transition is adopted between every two points, and a closed transition curved surface isformed; and the top surface, the bottom surface and the Bezier curve surface form a closed wedge-shaped structure entity. The gear shifting device is simple in structure and easy to machine, smooth gear shifting can be guaranteed, and a new way is provided for solving the problem that sliding is not smooth in the gear shifting process.