Parameter tuning of b0 is a difficult problem in active disturbance rejection control(ADRC). Therefore, a new method of parameter identification is proposed to identify the parameter of system, and a parameter tuning general law of linear active disturbance rejection control(LADRC) is presented. The influence of changing b₀ and b₀ on the closed loop system is investigated by using the frequency analysis method, and the robustness of LADRC is verified. Simulation results show that the proposed method works well, and LADRC has good performance to reject disturbance and has good robustness.