PFC-PID cascade transparent control strategy is presented with actions of typical electromechanical servo system. The random disturbance is surpassed in inner-loop with PID control, and the internal loop is the generalized control plant of the external PFC loop. The inner model of PID is the first-order plus the dead-time model which is gained by matching generalized control plant. The paper analyses the implementary arithmetic in the servo system with saturation and lag segment, and analyses the performance of the close loop to obtain the condition of stability and robustness. The simulation results show that the new PFC-PID control method is of robustness and the ability to suppress disturbance.