Magnetorheological damper (MRD), as semi-active vibration damping devices, has been widely applied in vehicle suspensions. Its response time has a significant impact on the performance of semi-active suspensions in heavy trucks. This paper investigated the electromagnetic response time of MRD and its impact on suspension performance. Firstly, the models of two-stage coils were established to analyze the influence of the coil structure of the MRD on the response time, and the dynamic response process was simulated by employing the finite element method. Subsequently, the dynamic equations of the half-car model of the six-wheel truck have been established and random road excitation generated through the filtered white noise method. Finally, the influence of different response time on the suspension performance, including the vertical motion of the vehicle body, the dynamic travel of the suspension, and the pitch angular acceleration of the vehicle body was studied. Simulation results show that in the double-coil structure, the reverse-series configuration exhibits shorter electromagnetic response time. The shorter response time of the damper can effectively enhance the ride comfort and handling stability of vehicles equipped with semi-active suspension systems with MRD, thereby providing a theoretical foundation for the engineering design and control strategy development of intelligent suspension systems in heavy-duty trucks.