Abstract: Based on the actual parameters of a wind farm which is integrated with Xinjiang grid. The PMSG model, which is based on d-q decomposition and hysteresis tracking method, and the wind farm equivalent model, which is based on the account wake effect equivalent velocity law, are built on the platform of PSCAD/EMTDC. A simulation is conducted on the characteristics of the short-circuit at the exit of the wind farm and its impacts on the differential protection of transmission line current integrated with the 110 kV grid under variations of wind speed, control strategy and fault type. The simulation results show that when a short circuit fault occurs outside the wind farm, the virtual value of short-circuit current provided by the wind farm is smaller than that of thermal power with same capacity but has strong volatility and has a significant influences on the protective devices at the PCC(Point of Common Coupling) of wind farms. Some improvement measures are proposed in view of the problems that may arise, which can provide a theoretical basis for large-scale integration of wind powers.