Abstract: The optimal disturbance rejection control law in a feedback and feedforward form is first proposed by using the solutions of a Riccati equation and a Sylvester equation.Then a reduced-order observer which can estimate the state variables and disturbances is constructed to make the feedforward control physically realizable.With combination of the reduced-order observer and the optimal feedback and feedforward controller,a design algorithm is presented for the dynamic output feedback disturbance rejection control law.Finally,simulations are given to demonstrate the feasibility of the presented control algorithms.