The multi-degree-of-freedom robot arm is a kind of widely used mechanical device. How to improve the response speed, tracking performance and anti-interference ability of the robot arm system has been the focus of research. Therefore, this paper is based on the classical active disturbance rejection technology. Firstly, the model establishment and control method selection of the 6-DOF series manipulator are completed. Secondly, the sliding mode tracking differentiator and nonlinear error feedback law are improved by combining sliding mode control and fractional calculus to improve the response speed and tracking performance of the system. A new type of nonlinear function is designed to construct an extended state observer, which reduces the high frequency flutter of the traditional extended state observer in application and improves the anti-interference ability of the system. Finally, on the basis of the established six-degree-of-freedom series manipulator joint model, the proposed control strategy is simulated. The results show that the response speed and anti-interference ability of the FRactional-order sliding mode active disturbance rejection controller are increased by 28.6% and 27.8% compared with the traditional active disturbance rejection control. It is verified that the proposed control strategy can effectively improve the response speed and tracking performance of the system, and has strong anti-interference ability.