Abstract: The variable-length dual-flexible manipulator is composed of a flexible joint and a flexible load， which is affected by flexibility， friction， and time variation of parameters. It will vibrate in the process of moving， which will reduce the tracking accu? racy of the end-effector. In this paper， the fuzzy tuning PI control strategy based on disturbance observer is used to control the out? put speed of the dual-flexible manipulator servo system. The vibration of the manipulator can be suppressed indirectly by control? ling the speed fluctuation of the flexible load. Based on the assumed modal method and the Lagrange principle， the dynamic equa? tions of the dual-flexible manipulator are established. A low pass filter in the disturbance observer is designed according to the ro? bust stability theorem， so that the disturbance observer can satisfy the stability of the controller parameter time-varying and the controlled object parameter perturbation jointly. The effectiveness of the proposed method is verified by numerical simulation and control experiments of the dual-flexible manipulator servo system. The experimental results show that the proposed control strate? gy can better eliminate the influence of parameter time-varying and flexibility on the output speed， and improve the control preci? sion of the end-effector.