To study the characteristics and influencing factors of inter-turn short circuit fault of excitation winding of hydro-generator, the fault mechanism of inter-turn short circuit of excitation winding was analyzed, and the expressions of excitation magnetomotive force and air gap magnetic density under normal and fault conditions of hydro-generator were deduced. On this basis, a two-dimensional finite element simulation model of the hydro generator was established by using the field-circuit coupling method, and the harmonic characteristics of the rotor magnetic field during the excitation winding inter-turn short circuit fault of the hydro-generator were obtained through the excitation winding inter-turn short circuit fault simulation.