<p>In order to enhance the trajectory tracking accuracy of the two-degree-of-freedom serial flexible manipulator system, an improved active disturbance rejection control method was proposed to conquer efficiently the impact of disturbance and chattering. Firstly, the dynamics model of the system was established according to the Euler-Lagrange dynamic formulation. Then, a new tracking differentiator is designed based on a S-type function, and the non-smooth function is reconstructed to continuous smooth function with the tangent function. Thirdly, the nonlinear states error feedback control law and an extended state observer are redesigned to obtain the improved active disturbance rejection control scheme. Simulation results show smaller chattering and higher tracking accuracy under the proposed control strategy.</p>