This article takes the external adjustment flap of an engine as the design optimization object with considera-tion on the results of scientific-research flight tests to simulate the load situation of the external adjustment flap during flight.It analyzes the causes of cracks and detachment faults.It proposes an optimization design scheme for the weak stress link of the external adjustment flap based on locating the damage on the external adjustment flap.The effective-ness of the optimization scheme has been demonstrated through simulation comparative analysis.