In the process of operation of a twinrotor turbofan engine, if inflection point of engine control plan changes, this may affect the engine performance. In order to study the influence of aeroengine performance degradation on the inflection point of engine control plan, a component level model is modified by component characteristics. A personalized degradation model of an aeroengine is built, and the effects of control plan inflection point advance and major component decline on engine performance are analyzed. The decline of engine components is studied, and the change of exhaust temperature is analyzed. The research result shows that with the deterioration of turbofan engine components, the exhaust temperature increases, and this makes the inflection point of engine control plan moving forward. And, the inflection point of engine control plan moves forward greatly after the engine performance declines. The forward movement of the inflection point of the control plan causes the thrust loss of the engine at the maximum state to reach 3.65% of the total state of the engine when the engine is not in recession. The thrust is reduced by 0.5% compared with engine degradation on no consideration of the change of control plan.