Servo controller is a fundamental component of the optical storage system. Processing the signal error between optical pick-up head (OPU) present position observed by the photo detector and the next position instruction, the controller generates a control signal which drives the motors in OPU. A new servo controller based on the sliding-mode variable structure control theory is researched. By means of building a physical model of the objective, the servo controller develops the state-space functions. A corresponding sliding-mode switching surface and the reaching law are also designed, and the inner-loop controller and outer-loop controller are finally designed. Compared with the classic controller based on phase correction theory, the simulation results show smaller overshoot and set time of the step response, which proves better response and robustness of the controller by increasing limited resource consumption.