In order to improve steering stability of the vehic le, a 3-DOF bus rollover dynamics model is establis hed ， and the vehicle steering stability controller is designed, and a kind of easy sliding mode control strategy ba sed on linear matrix inequality (LMI) is proposed. Using Matlab/S imulink, the simulation results show that the propo sed sliding mode control strategy can effectively reduce roll a ngle velocity, roll angle, side-slip angle and stab le yaw rare, and thus improve the vehicle steering stability.