Abstract: Choosing appropriate weighted functions in the frequency domain,and in combination with the state-space model of the real plant,the formulation of the state-space model for some generalized plant by employing the method of loop shaping and internal principle was established.The original control problem was converted to a standard H_∞ problem.The controller for the original plant was derived by means of solving optimal H_∞ dynamic output feedback controller for the generalized plant based on Linear Matrix Inequality (LMI).This design procedure was applied to a turbo-fan engine.The controller obtained by this method was verified in a wide engine operating range in the flight envelope.Simulation results of the turbofan engine nonlinear model show that the characteristics of the controller,namely,tracking characteristics,disturbance rejection and robustness,are satisfactory.