Abstract: The reliable operation of the outer pipelines of aero engines directly determines the safety of the engines. During the 150 lasting mapping test, an engine air pipe fractured. Macroscopic inspection and metallurgical analysis were carried out to find and analyze the fault causes. Based on the analysis results of higher stress at the welded joint of the pipe, stress calculation and measurement were carried out to obtain the stress of the pipe during actual work. The results show that the pipe has multiple natural frequencies and the problem of large resonant stress in the steady working range. After the partial optimization of the mounting base structure of the air pipe and the improvement of the pipe shape, the whole machine passed the 60 h examination and 150 h lasting test successfully, and the whole machine test of more than 600 h was completed in total, without any crack or fracture, which verified the effectiveness of the improvement measures.