In order to meet the requirement on voltage of wind farm PCC, at the same time reduce the voltage difference at each wind generator end, a control strategy for reactive power that applying Genetic Algorithm is given. In time-scale, this strategy calculate reactive power demand of wind farm by monitoring the voltage of PCC, while considering the PV characteristics of wind farm and the reactive power ability of DFIG. In space-size, this strategy determine allocation scheme of each DFIG using Genetic Algorithm. Example shows that the proposed strategy can effectively reduce the voltage difference of each DFIG terminal, while keep the PCC voltage tracking of grid requirement.