To address the inadequacy of traditional constant-speed control methods in adapting to extreme mountainous conditions, this paper proposes a variable-speed coordinated longitudinal-lateral control strategy based on the coupling characteristics of vehicle dynamics. The strategy adopts a hierarchical control structure: the upper layer designs a steady-state evaluation model to provide an accurate decision-making basis for the middle and lower layer controls; the middle layer primarily utilizes a two-level Model Predictive Control to coordinate potential conflicts between longitudinal four-wheel slip rates, lateral Active Front Steering and Direct Yaw Control, and outputs the total driving torque and yaw moment; the lower layer employs Weighted Least Squares to optimally distribute the obtained torque according to the vehicle's operating state. Finally, a simulation model of the designed coordinated control strategy was established based on the Simulink and CarSim simulation platforms, and various complex road conditions were simulated for verification. The results demonstrate that this control strategy can significantly improve the driving stability of distributed electric vehicles under variable-speed extreme conditions.