In this paper we propose a control scheme of electromechanical actuator with optical encoder feedback. Controlled object is the simplified model of a DC motor while feedback device is an optical encoder. Encoder model is established after analyzing its principle and signal characteristic. Many velocity estimation methods have been compared and the least squares fit filter is selected for our design because of its simple algorithm and capability of predicting velocity and position. Using these predictions as feedback, a variable structure controller based on exponential approach law is adopted in the actuator close-loop control. The relationship between system performance and encoder resolution is exposed. This scheme can be implemented easily with low cost and convenient interface. Its validity is proved by simulation results.