Abstract: A third-stage rotor blade of the high-pressure compressor in an aero-engine was found to have lost an angle after testing. The failure mode and factors were analyzed by fracture surface analysis, microstructure examination, and mechanical properties testing. The results show that the fracture surface presented the characteristic of multi-source fatigue. The crack initiated from the back side of the blade. No metallurgical and machining defects were found at the fracture source zones. However, obvious collision and friction trace can be seen on the fracture surface. The fracture became smooth because of the collision and friction. No other new elements other than the matrix elements in TA11 alloy were detected by EDS. It is assumed that long time asymmetrical collision and friction between the blade and casing increased the vibration and induced the sympathetic vibration, which led to the initiation and promulgation of the fatigue crack. Finally, angle loss happened.