Abstract: According to the physical meaning of the H∞ norm,a nonstrict proper model is converted into some strict proper model under the equivalence condition of their H_∞ norms.A static output feedback PI controller for the resulting strict proper model is designed on the basis of LMI,and control constraints are taken into consideration in the design process of the controller.An algorithm for solving the static output feedback PI controller is presented.This method is applied to the design procedure of aero-engine controller.The dynamical and static performances of the aero-engine control system are verified at different partitioned regions of flight envelope.