Abstract: Abstract: To solve the problem of the contradiction of improving riding comfort and handling stability of suspension system at the same time with active control algorithm, the active disturbance rejection control was selected and improved to lower suspended mass acceleration and dynamic load of tire of suspension system simultaneously after the consideration and comparison of 4 kinds of control algorithms, which were based on state, classic control theory, optimal control theory and intelligent optimization theory, respectively. Suspended mass acceleration and dynamic load of tire were combined as the feedback signal, which was compared with the reference input signal to generate the state error, and then a nonlinear state error feedback control law was provided which took all the terms of proportion, integration and differentiation of state error into consideration. A comprehensive performance assessment criterion on suspension system was established considering both suspended mass acceleration and dynamic load of tire, and it could be used to assess the effectiveness of the improvements on suspension system comprehensive performance with the improved control algorithm. The formula of comprehensive performance assessment criterion was established based on quartic power function, which could magnify the effect of control algorithm on different vibration features of suspension system and different riding performances of vehicle. Then a parameter tuning method of the improved active disturbance rejection controller was stated based on the analysis on the functions and influences of different parameters, the reference ranges of which were provided for effective design of control algorithm. Simulations were made to compare and analyze the performance of the standard skyhook active control suspension system, the standard active disturbance rejection control suspension system and the improved active disturbance rejection control suspension system. The results showed that: 1) Both suspended mass acceleration and dynamic tire deformation of suspension system were reduced by 17.68% and 1.78%, the riding comfort and handling stability of vehicle were more advanced with the improved active disturbance rejection control compared with the standard skyhook active control and the standard active disturbance rejection control, and the comprehensive performance of vehicle with the improved active disturbance rejection control was much better than that with the other two; 2) As to the analysis in frequency domain, the transmissibility of suspended mass acceleration of suspension system with the improved active disturbance rejection control could be depressed in low resonance frequency range, medium frequency range and high frequency range, and both the transmissibility of dynamic tire deformation and the suspension working space with that could be suppressed in low resonance frequency range, which were the major working ranges in improving the transmissibility of suspension system; 3) All the relative fluctuations of riding comfort, handling stability and comprehensive performance of vehicle with the improved active disturbance rejection control algorithm were less than 2%, 4% and 2% respectively as the variation of suspended mass, road excitation level and vehicle velocity, which indicated the robustness of the improved active disturbance rejection control was the strongest one among them. Bench tests of suspension system were conducted to compare and analyze the performances of the passive suspension system and the improved active disturbance rejection control suspension system. The results showed that: 1) All the measured data were a litter larger than the simulation data because of the differences between simulation parameters and bench parameters, the measurement noise and the non-adhesive feature between the springs and the masses; 2) Both suspended mass acceleration and dynamic tire deformation of suspension system were lowered with the improved active disturbance rejection control in experimentation, and the comprehensive performance of vehicle was improved remarkably, which fitted the simulation results; 3) All the relative fluctuations of comprehensive performance of vehicle with the improved active disturbance rejection control were lower than 3% as the variation of suspended mass, road excitation level and vehicle velocity, which demonstrated the strong robustness of the improved active disturbance rejection control algorithm.