A control scheme consisting of a disturbance compensation method and an improved sliding mode controller was proposed to improve the disturbance rejection rate of the stabilized platform used in a seeker. Firstly, the disturbances were divided into friction torque and rest disturbances. The friction parameters based on the Stribeck friction model were identified. An extended high-gain observer was designed to estimate the rest disturbances in the system dynamics, and the convergence condition of the estimation error was set. Meanwhile, the peaking phenomenon of the observer was reduced by saturating the estimates. Then, an improved sliding mode controller was chosen to control the servo system, and a Lyapunov-based analytical method was employed to ensure the convergence of the tracking error. Lastly, experiments on the stabilized platform and the seeker were carried out to validate the control scheme. By using the proposed control scheme, the dead zone at low angular velocity caused by friction was eliminated, and the steady precision was increased by 0.032 8 (°)/s, when tracking a trapezoidal wave of 1 (°)/s. In addition, the disturbance rejection rate was increased by a minimum of 0.57%, when the three-axis turntable was disturbed by typical disturbance conditions. It can be concluded that the control scheme can improve disturbance rejection.