As one of the important components of aircraft engine, the exhaust tail pipe is mainly welded from thin plates. Due to the longterm harsh conditions such as high temperature, vibration and air flow, exhaust tail pipe failure accidents often occur, and the weld often cracks as the weak part of the exhaust tail pipe. Two cracks were found in the exhaust tail pipe on the aircraft during routine inspection after the flight. The causes of cracking were analyzed by macroscopic inspection, fracture surface morphology analysis and microstructure analysis. The results show that due to the structural design reasons, there are multiple welds at the same position on the exhaust tail pipe, which is a structure with multiple dense welds, making the welding joints overheat, and the ferrite in the weld structure presents a netlike distribution. At the same time, there is a welding burnthrough on the welding joint, which leads to the decrease of the mechanical properties of the welding joint and the initiation and expansion of fatigue crack; the support screw and the reinforcing rib are not fully welded, and the arc is connected at the point instead of the surface. During the flight, the vibration stress concentration and fatigue cracks initiation occur at this position, and finally fatigue failure occurs.