<p>Electric vehicles (EVs) constitute a complex mechanical system subjected to multiple external excitations during operation, including road irregularities and excitations originating from the integrated electric drive system (IEDS). The resulting vibrational responses exhibit strong coupling and mutual interactions among key components such as tires, suspension, vehicle body, and the integrated powertrain. However, existing dynamic models inadequately capture this vibrational coupling mechanism in a comprehensive and accurate manner, thereby limiting further research and system optimization. To address this limitation, this study develops an integrated vehicle—road coupled dynamic model for an EV equipped with an IEDS, based on existing research. The proposed model effectively reveals the strong coupling relationship between the dynamic responses of the electric drive assembly and the vehicle body. Furthermore, it systematically investigates the impact of road irregularity and vehicle speed on the dynamic performance of the IEDS. On this basis, a particle swarm optimization algorithm was employed to optimize the design of the mounting points in both x and y directions, resulting in significant improvements in the dynamic performance of the system. The comprehensive model presented in this study enables a more thorough and realistic analysis of the dynamic characteristics and coupling mechanisms of the electric drive system, which allows for the prediction of system vibration responses under various road conditions and driving scenarios, thereby providing valuable guidance for the coordinated design of suspension and powertrain systems. It holds certain theoretical importance and applied engineering effect for enhancing the NVH performance and mechanical reliability of EVs.</p>