The invention provides a double-fed wind turbine generator set-based wind farm reactive power control method. The method includes the following steps that: wind turbine generator sets in a wind farm are divided into a plurality of reactive power adjustment and control units according to adjustment and control priorities, so that the reactive power demand of the wind farm can be obtained; the adjustable reactive power capacities of the reactive power adjustment and control units and reactive power compensation devices are calculated, and reactive power distribution is performed on the reactive power adjustment and control units and the reactive power compensation devices according to the reactive power demand of the wind farm; and whether the grid-connected point voltage of the wind farm is in a permissible operating range is judged. According to the method provided by the invention, the electrical wiring of the wind farm and the influence of characteristics of voltage distribution in the wind farm on the reactive power adjustment ability of the wind turbine generator sets and grid-connected point voltage supporting effects are considered, and the reactive power adjustment ability of the wind turbine generator sets can be optimized, adjusted and controlled, and accurate, reliable and effective support can be provided for the voltage of the wind farm and a system; and the reliability and efficiency of double-fed wind turbine generator set-based wind farm grid-connected operation can be ensured.