In order to study the impact of short circuit fault on grid connected operation of wind farm, the equivalent method of wind farm, which consisted of doubly fed induction generators (DFIG), was analyzed based on the Single model of DFIG. The power system model including a DFIG wind farm was built up by EMTP-RV. And this paper also investigated the characteristics of grid connected operation of DFIG wind farm, such as the output characteristics of active power and reactive power under the condition of single-phase short-circuit and three-phase short-circuit of power system, the bus voltage fluctuation at the public connection point of grid and the transient change of system frequency. The result has an important guiding significance and reference value for the project construction of wind power in the future, as well as the wind farm in operation.