Abstract: Large-scale centralized development and utilization of wind energy are widely adopted in China. Therefore, the output current of wind farm is generally very large during faults. The current characteristics play an important role in the setting calculation and reliable operation of the relay protection. In the period of faults, the output current is related to the operating status of DFIGs, low voltage ride-through (LVRT) and control strategies. The current frequency characteristics of DFIG-based wind turbines are discussed in this paper. When the crowbar works with the voltage severely dropped, the interharmonic component appears in the output current. The initial amplitude of the interharmonic component is related to the voltage drop, the crowbar resistance, the slip and the initial active power and the decay speed is rapid. When the inverter works with the voltage slightly dropped, the second harmonic appears. The initial amplitude is related to the initial value of the fundamental frequency component and the PI controller coefficient. The decay speed is slower than the interharmonic component. In the case of an asymmetric fault, the negative sequence component makes the third harmonic appear. The third harmonic component always exists until the fault cleared. The main non-fundamental frequency components in the output current are studied by the quantitative calculation method of DFIG models in order to be made full use of, which helps the relay protection to improve the protection criteria. as a consequence, we can improve the performance and applicability of relay protection effectively, which has important guiding significance for the development of new relay protection principles.