Abstract: By analyzing the cases of rotor cracks in turbine-generator units at home and abroad, the crack faults are found to be caused mainly by vibration, stress concentration, thermal stress and environmental corrosion, etc. Development tendencies of both the vibration and cracking are revealed, while the basis for fault diagnosis of rotor cracks proposed. Countermeasures for prevention of rotor cracks are simultaneously put forward, such as reducing the times of peaking operation, prolonging the warming-up period during start-up and shut-down, controlling the vibration level and concentrating on examining the areas where cracks frequently occur.