The inter-turn short-circuit fault of the generator rotor winding is seriously threatening the safe and stable operation of the electrical main equipment of the power plant due to the frequent occurrence, the difficulty of fault diagnosis and the serious consequences of the fault. Therefore, how to diagnose the fault of large turbo generator rotor winding inter-turn short circuit becomes one of the most difficult problems to be solved in power industry. In this paper, the causes of short-circuit faults in the rotor turn, the classification of faults and the analysis and diagnosis methods of faults are first introduced. Then, based on the case of short-circuit faults occurring in the rotor windings of the 1 000 MW turbine generators that have just been put into production. The diagnosis method and process of the inter-turn short circuit fault of the rotor are explained. According to the results of the electrical test and the on-site inspection, it is determined that the insufficient copper wire grinding at the corner of the rotor coil is the main cause of short-circuit faults between the rotor turns.