Vehicle lateral motion control technology is the cornerstone of autonomous driving, and the influence of the road curvature on control performance is worthy of attention. This paper proposes a robust lateral motion controller and analyzes the effect of the road curvature on control performance. Firstly, the lateral motion controller is designed based on the suboptimal ℋ ∞ control. The ℋ ∞ control problem is transformed into the feasibility problem of linear matrix inequality. Then, an algorithm considering different dimensions of the tracking errors is proposed to search for feasible candidate controller gain. The appropriate controller gain is chosen considering the anti-interference and lateral motion control performance. Finally, co-simulations with Simulink and CarSim are performed. The effectiveness and robustness of the proposed controller are demonstrated via the comprehensive analysis of time domain and frequency domain.