Abstract: A back-stepping terminal sliding mode control strategy was proposed based on nonlinear disturbance observer (NDO) to address the composite interference problems caused by un-modelled dynamics and parameter perturbations during the operation of a multi-stage hydraulic erecting system. Considering the unknown parts of the system model and external disturbances as lumped disturbances, a nonlinear disturbance observer was designed to observe the lumped disturbances of the system, and a back-stepping terminal sliding mode controller was developed based on the observed values. And then, the stability and convergence of the proposed control method were demonstrated. Finally, according to Matlab/Simulink simulation, the control effects of the proposed method were compared and analyzed with that of traditional sliding mode controllers and traditional sliding mode controllers based on disturbance observers. The simulation results show that the proposed method can effectively improve the displacement tracking performance of multi-stage hydraulic cylinders during the operation of hydraulic erecting systems.When disturbed, the displacement tracking error of the system can quickly approach zero, demonstrating better tracking robustness.