Hydraulic servo system has been widely used because of its high control precision and high power density. However, it has large disturbance and nonlinearity in real-world operation, its precise position control is difficult. Active disturbance rejection controller (ADRC) is a new type of controller, which has good control ability under strong uncertainty and nonlinearity, but ADRC is a multi-parameter nonlinear controller, its design is much more difficult than PID and other traditional controllers.An improved differential evolution algorithm was proposed. A new objective function was used in the design of adaptive active disturbance rejection controller for hydraulic servo system. The simulation results show that the improved differential evolution algorithm has stronger global search ability than other methods, and the designed ADRC can meet the needs of hydraulic servo control.