Abstract: Considering the harmfulness of electromagnetic interference(EMI) on the full authority digital electronic control FADEC system of turbofan engine and aiming to address the demands of backup hydraulic mechanical control system of FADEC, a general design method of turbofan engine hydro mechanical steady-state controller was proposed, which was based on the modular design ideas of the closed-loop control loop transfer function to describe the internal characteristics of the linear constant system with specified input and output, and based on the invariance of superposition principle of multiple-input single-output linear system. The PI control structure with variable integral gain was adopted to isolate the steady-state controller in the closed-loop control loop according to the input-output relationship of the transfer function. The separable controller module with the rotor speed error as the input and the fuel flow command of the actuator as the output was extracted to realize the universal design of the hydro mechanical steady-state controller for turbofan engines.