Aiming at the model of projectile transfer arm electrohydraulic servo system with parameter uncertainties and nonlinearities, a parametric adaptive backstepping control algorithm was proposed by combining backstepping control design method and adaptive control method. The backstepping control design method was used to derive the control law of the nonlinear system, and the global stability of the closedloop system was proved by combining with the Lyapunov theorem. Aiming at the uncertain parameters of the model, the discontinuous mapping adaptive law was constructed for accurate estimation,so the uncertainty problem of the system model was solved and the design of the control algorithm was simplified. The robust term was introduced to improve the system stability. The simulation results show that the designed algorithm is effective and has better control effect than the PID algorithm.