Abstract: For a 600 MW subcritical Turbo-generator Unit, the first start-up succeed, but the second and the third start-up failed due to the vibration was too large. By analyzing the operating parameters and the vibration data, the result that the rotor was bending was proposed. When the bending restored to normal through barring and then some measures were taken,the fourth start-up succeed. There is reference significance for other units' start-up

Key words: steam turbine, bending, serious vibration, failed start-up