Abstract: This paper presents the use of sliding mode (SM) observer to detect vehicle sideslip angle.Tangent function is used in SM observer to cover chattering effects.The SM observer utilizes a 2DOF single track model as the basis for the mode detection.The experimental data are acquired from a light SUV,a multi-DOF vehicle model in veDYNA dynamic simulation software.Double lane change maneuvers are designed to verify the performance of the SM observer.Simulation results point out that compared with Kalman filter,the proposed SM observer has better performance on its accuracy on vehicle sideslip angle estimation.