In order to improve the lateral stability and driving safety of tractor-trailer combination,a tractor-trailer combination model considering active torque control was built,and the minimum of the sum of rear amplification factor ( RWA) and sideslip angle was used as a fitness function for the genetic algorithm to design an linear quadratic ( LQR) controller,by which the optimal active torque was obtained and then feed back to the vehicle model.As compared with the vehicle model without LQR controllers,the proposed model with active torque control can avoid the snaking of the dolly and the second semitrailer,reduce the RWA by 7. 9%,and help each unit of the vehicle combination to quickly reach a steady state.However,the proposed strategy for sideslip angle control in each vehicle unit is not as precise as for yaw rate control.