<p>In robot control systems, backlash is a common nonlinear factor in transmission links such as gears. The discontinuity and hysteresis effects it produces will destroy the accuracy of the system, leading to increased trajectory tracking errors, delayed response, and even system oscillation or decreased stability. Aiming at the problem of low tracking performance of robot manipulators under external disturbances and backlash, a sliding mode control method of trajectory tracking for manipulators with backlash is proposed in this paper. Firstly, to prevent problems at one joint from affecting the performance of other joints, a decoupling system based on inverse dynamics is used to keep each manipulator joint as independent as possible. Then, the second-order sliding mode controller is designed by combining the non-singular fast terminal sliding mode with the improved super-twisting algorithm. The discontinuous terms are put into the integral, which makes the control more stable and the response faster. Secondly, to prevent the collision between the motor and the joint of the manipulator, the acceleration observation compensator is used to compensate for the shaft torque when the manipulator passes through the unknown dead zone. Finally, a three-degree-of-freedom robot manipulator is used as the research object. The simulation results showed that compared with the existing double-terminal sliding mode control (DTSM) method, the control method proposed in this paper improved the tracking accuracy of joints 1, 2, and 3 by 88.68, 75.18 and 63.94%, respectively, proving its effectiveness and superiority.</p>