The rotor windings interturn short circuit fault is one of the common faults in turbine generator. When a generator runs in asymmetric condition emerging negative sequence magnetic field, the deterioration rate of interturn short circuit fault in rotor windings can be accelerated. In this paper, a 300 MW turbine generator running under asymmetric operation was studied as an example. Considering damping system, the variations of generator fault characteristics after rotor winding interturn short circuit were studied, including rotor current, rotor winding induced electromotive force, short circuit loop current and damping current. What’s more, the influences of rotor short circuit coil turns and pitch and shortcircuit point transition resistance under negative sequence magnetic field on the rotor short current were studied, also the heating condition of the short circuit point was roughly analyzed. The results provided a reliable decision support for repairing interturn short circuit in rotor winding after a generator experienced bad operating conditions.