Abstract: A method was proposed for a robust H_∞ autopilot to make the UAV controller easy to apply and able to handle its performance degeneration due to uncertainties caused by parameter variation and external disturbance. Firstly, a linear UAV model was developed to depict the UAV movement, a state space expression was formed, a generalized controlled object was set up and a controller was designed based on robust H_∞ theory. Then, a series of systematic test was taken for the developed controller, the controller model was discretized and reorganized for the hardware condition, and the control C code was imbed into microprocessor to execute real time simulation. The semi-physics simulation results indicate that, the UAV with autopilot can track a reference signal exactly, the movement parameters suit for the design specification, the robust H_∞ autopilot can be used for the UAV controller.