Aiming at the problem of uncertainty and input saturation for electro-hydraulic position servo system, an adaptive anti saturation control strategy was proposed.The mathematical model of a valve controlled cylinder system was established;in the design framework based on backstepping, the tracking error caused by input saturation was added to the Lyapunov function, and the controller was designed according to this Lyapunov function. By making the Lyapunov function asymptotically stable, the tracking error of the system was converged to zero. For the uncertain parameters in the system, the adaptive algorithm was used to update them iteratively to ensure the effectiveness of the controller. Taking the minimum tracking error as the objective function, the particle swarm search algorithm was used to optimize the four parameters of the controller. The results show that the amplitude of anti saturation control signal is significantly reduced compared with that without input saturation, and the input saturation phenomenon is eliminated; under the condition of parameter uncertainty and input saturation, the maximum tracking error of hydraulic cylinder is only 5.8×10-6mm, compared with no anti saturation algorithm, the tracking error is greatly reduced.