Abstract: This paper presents relevant inspections conducted on the centrifugal casing scuffing fault of a certain auxiliary power unit during a high-altitude simulation test. The fault tree analysis method was used to investigate the fault. The analysis results show that the scuffing failure is caused by multiple factors, including excessive residual unbalance of the rotor and insufficient design clearance between the inner labyrinth teeth of the sealing sleeve and the lock nut. With targeted improvement measures implemented, the scuffing fault was ultimately eliminated. The above research findings can provide valuable experience for the subsequent development of related models.