A dynamic model with bend-torsion coupling was established for helical cylindrical gear split-torque transmission system of heavy load (above 10KNm), in which the time-varying mesh stiffness, random backlash, mesh error and bending deformation of shaft were considered. Express the bending stiffness, the torsional stiffness and the damping coefficients of the dynamic equation using dimension parameters, this model could provide more precise guidance for design work. Acquire the sharing coefficients and the dynamic coefficients, through solving the dynamic equation of system by the fourth-order Runge-Kutta method. The results show that reduction of the diameter of transmission shaft could effective improve the load sharing performance of system; Dynamic factor will fluctuate while the diameter of transmission shaft be smaller than a threshold value; Dynamic coefficients will be reduced while the moment of inertia of the bigger gear on transmission shaft is decreased properly.
