In order to study the coupling effect of cylindrical gear dynamics and elastohydrodynamic lubrication (EHL), based on dynamic theory, a dynamic model of a six degrees-of-freedom (6DOF) coupled system is established. Based on the numerical solution of EHL, an improved dynamic transmission error (DTE) model was established. The oil film stiffness, oil film damping, and center oil film thickness obtained by the numerical solution were used in the gear dynamics analysis. The dynamics and EHL characteristics of the gear system are analyzed and compared with the general model. The results show that by using the improved DTE model, the comprehensive stiffness and comprehensive damping of the gear increase and fluctuate slightly. The amplitude of the tooth surface meshing force and dynamic response decreases. Under the action of tooth surface meshing force, the oil film pressure and thickness show oscillation characteristics.