In order to explore the calculation and change law of the time-varying friction force of helical gears under high-speed and heavy-load,based on the conversion relationship between the principle of minimum elastic potential energy and kinetic energy,a time-varying load calculation model was proposed,and the friction parameter model such as the length of the time-varying contact line and the friction coefficient were calculated and analyzed.The slicing method was used to derive the time-varying friction formula,and the calculation results were compared with those of existing algorithms.The MATLAB software was used to calculate and analyze the change of the maximum time-varying friction force under high-speed and heavy-load conditions in the same cycle.The results show that the time-varying friction force derived based on the time-varying load model while considering the time-varying friction coefficient fluctuates is larger than that under constant meshing force,the calculation result is closer to the actual situation,and the calculation is more accurate,and under high-speed and heavy-load conditions,the increase of load torque and speed can increase the friction.