This paper proposes a hierarchical structure reactive power control strategy to solve the voltage stability problem caused by wind farm integration. The reactive power demand of the wind farm is calculated based on the deviation of reference voltage and measured voltage at the control point. The target reactive power for each individual wind turbine is calculated using the equal power factor algorithm. In this way， the voltage stability of grid integrated wind farms can be improved. The reactive power and power factor limits are considered in real time during the whole control strategy process. Simulation results on the New England 39-bus system show that the presented strategy can support the voltage at the control point and can restrain voltage dips caused by local network faults.