The small diameter turbodrill reducer is an important part of the tool for deep hole drilling. Replacing traditional gears with asymmetric gears is an effective way to increase the load capacity of the reducer. The root radius and pressure angle on the working sides of the asymmetric gear are the key parameters of the symmetric gear. In order to further study the influence of the root radius and the pressure angle on the working side on the bending stress, the solar gear in the 127mm diameter turbodrill reducer is used as the research object to establish a force model of the asymmetric gear with the theoretical calculation formula for the bending stress of the asymmetric gear. established by the plane cross section method. Through the finite element method, the symmetrical gear and the asymmetric gear are compared and analyzed. The simulation results show that as the root radius increases, the radius of curvature of the gear root transition curve increases; thus, improving the bending stress concentration. Increasing the pressure angles on the working side can effectively reduce the bending stress; however, when the pressure angle exceeds a certain value, the bending stress gradually tends to be stable. The theoretical analysis is in good agreement with the simulation results, and the research conclusions can provide the basis and reference for optimizing the main parameters of the asymmetric gear.