As to the mutual effect of wake turbulence among wind turbines in a wind farm with wind turbine driven doubly fed induction generator (DFIG), a new equivalent modeling method is proposed. This method considers the wake effects of wind turbines and defines the wake effect factor which shows how one wind turbine is affected by the others. This method also uses this factor as a grouping rule of wind turbines. Using wind direction as input, the calculating method groups the wind turbines and aggregates the same group. The calculating method of equivalent model parameters is provided, thus a wind farm model which is represented by few wind turbines is obtained. Compared with the traditional equivalence model, the simulation results show that the equivalent model based on the proposed method describes the power output of wind farms more accurately.