In order to study the impact of sub-optimal controller on road-friendliness of vehicle active suspension system,a simple 2-dof 1/4 vehicle model was constructed and the random optimal and sub-optimal controllers were designed.The simulation models of passive suspension,optimal active suspension and sub-optimal active suspension were established with Matlab/Simulink software.Then,the road-friendliness of these suspensions was analyzed and compared.The simulation results show that,the road-friendliness of sub-optimal control suspension after rational design,which is close or equal to optimal control suspension,is better than that of passive suspension.Hence,the sub-optimal control suspension has better engineering application values.