In order to reduce complexity of simulation model of wind farm while ensuring accuracy, and considering wake effect and different control methods in actual wind farm, a two-step clustering method based on Analytic Hierarchy Process is proposed. Both initial operating point and dynamic behavior are considered in this method. Firstly, the input wind speed is calculated under the influence of wake effect. The first step clusters the DFIGs according to pitch angle action situation, and the second step re-clusters the DFIGs by their dynamic characteristics according to disturbed curves of rotor current. Then parameters of equivalent wind turbine generators and collecting power lines are derived respectively to ensure power output characteristics and voltage difference constant. Thus a multi-machine equivalent model of wind farm is obtained. Finally the proposed equivalent method is validated by simulation results.