Abstract: An electro-hydrostatic actuator (EHA) is a typical mechanical/hydraulic system suffering from high level of nonlinearity and parametric uncertainties. In this paper, based on sliding mode control (SMC), a novel control scheme, adaptive damping variable sliding mode control (ADV-SMC) was proposed to handle the preceding uncertainties. The method overcame the influence of friction and external disturbance by the robustness of sliding mode control. And variable damping method was used to suppress the overshoot of step response. The parameter adaptation law was driven by tracking errors. The task of the robust item was alleviated due to the presence of parameter adaptation. Consequently, the tracking performance was further improved. Besides the theoretical proof of an asymptotic tracking performance, numerical experiments were also conducted to verify the effectiveness of the proposed method.