The purpose of this article is to study the impacts on engine performance caused by the engine deterioration after long time use

and the result was used in the engine performance margin design in new developing engines.Method is to use data acquired in special arranged performance-deterioration engine tests as well as the ones collected from overhauling engines

to analyze the impacts on engine performance caused by module efficiency loss

and to find out the difference between new delivered and deteriorated engines.This difference is used to the engine performance calculation after deterioration in development engines.Conclusion: the performance margin of 100 ℃ in engine gas temperature(EGT) and 7% in specific fuel consumption(SFC) need to be maintained in subject new development engines in order to guaranty the safety use within the time between overhaul

and development engines can meet the higher performance requirement of new generation aircraft relying on the efficiency improvement in modules.