Aiming at the problem of model uncertainty caused by the change of flight conditions, robust pitch attitude control system is designed using μ control theory. The pitch attitude control system design is constructed into the general framework of μ synthesis according to the principle of interference suppression. And the robust performance problem is transformed into robust stability problem of augmented system. Secondly, the D-K iteration algorithm is used to solve the fourteenth-order controller. Then controller is reduced to fourth-order successfully using the balanced truncation model reduction procedure. Lastly, robustness analysis is performed in terms of the reduced-order μ controller. The reduced-order μ controller yields the desired robust stability as well as the robust performance.