Abstract This paper presents a detail research on a vibration high fault after overhaul occurred on a generator. During the overhaul, the generator rotor is returned to factory for processing and replaces section across the line of the generator excitation end. The gas turbine unit vibrates high in the idle 3000 r·min −1 and full load. The large vibration of the generator is mainly caused by the following two factors:the imbalance in the overhanging end of the generator rotor and the electrical fault in the generator itself. The unbalanced amount of generator overhang was successfully eliminated by dynamic balance test. The electrical fault of generator itself needs to be returned to the factory to handle.