In this study, an adaptive servo controller based on LQR is designed for flexible master-slave system (FMSS). A dynamics model, observer and servo controller based on LQR is built respectively. According to the parameter sensitive experiments, adaptive servo controller based on LQR is designed. This research focuses on the performance of rapid response and vibration suppression. Experimental results indicate that adaptive servo controller, which suppresses the saturation of the input torque to ensure the stability, has achieved short time delay and adequate vibration suppression.