Tooth profile deviation is one of the main factors causing vibration and noise in transmission systems. In order to explore the influence of the randomness of tooth profile deviation on the dynamic characteristics of spur gears, this paper conducted a study on the nonlinear dynamics of spur gear pairs based on random tooth profile deviation. Firstly, based on the consideration of the characteristics of tooth profile deviation, combined with the tolerance constraint characteristics of gear tooth profile, the variation characteristics of random tooth profile deviation under a certain tolerance were analyzed. Secondly, based on the TCA (tooth contact analysis) method, the solution method for the meshing error of spur gears was studied, and the influence of random tooth profile on meshing error was explored. Finally, based on the previous meshing error solution method, a nonlinear dynamic model of spur gear considering multi tooth meshing state was constructed, and the influence of the randomness of tooth profile deviation within a certain tolerance constraint range on the dynamic characteristics of spur gear transmission system under different working conditions was analyzed. The results indicate that the research method proposed in this article can be used to analyze the effects of different tooth profile deviations and their randomness on the meshing of gear teeth, providing a reference for predicting the impact of tooth profile tolerances at different accuracy levels and designing gear accuracy.