In order to solve the nonlinear problems caused by hydraulic system leakage, nonlinear friction of components and external load changes in the hydraulic servo system of a blasting launching platform, a control method based on disturbance observer and Terminal sliding mode control was proposed. The disturbance observer is used to observe the system disturbance and reduce the influence of the disturbance on the stability of the system, and the sliding mode control with strong robustness is used to eliminate the influence of the internal nonlinear uncertainties of the system. Aiming at the defect that the tracking error of the traditional sliding mode control can not converge in a finite time, the Terminal sliding mode control of a nonlinear system is adopted to achieve the tracking in a specified time. The simulation and experimental results show that the control strategy can effectively improve the position accuracy of the launch platform, and the system has strong robustness.