Aiming at the problems of uncertain parameters,external disturbance and unmeasurable system state of valve-controlled electro-hydraulic position servo system,an adaptive backstepping sliding mode control strategy with ESO (extended state observer) was proposed based on backstepping control and sliding mode control theory.The nonlinear state space equation of the system was established,and an ESO was designed based on the system model to estimate the velocity and external disturbance effectively.At the same time,the adaptive algorithm was introduced to estimate the uncertain parameters of the system online,and the adaptive law of the uncertain parameters was designed.The stability of the designed controller was proved by Lyapunov stability theorem.Finally,the simulation results show that the designed controller can effectively estimate the velocity and external disturbance,and it has high-quality position tracking ability.