For a class of uncertain timedelay system, the uncertainty of the system states and the fragile of the controller were considered,a robust nonfragile H∞ controller for uncertain timedelay systems based on state observer was designed in the case that the system states could not be obtained directly. The controller was applied to the trajectory tracking control simulation for the robot manipulator servo system. By observing and tracking the state information of robot manipulators, such as robot manipulators angle and angular speed, the effectiveness of the state observer and the feasibility of robust nonfragile H∞ control were verified.