The invention provides a reactive voltage control system of a wind farm of a doubly-fed set. The system comprises dispatching center equipment, a wind farm power management module and a plurality of blower controllers. More specifically, the dispatching center equipment is used for obtaining a given value of a reactive power of a wind farm by calculation according to a control point voltage and an active power of the wind farm and a reference voltage, wherein the control point voltage and the active power are obtained in real time; the wind farm power management module is used for distributing the given value of the reactive power on the wind farm; and the plurality of blower controllers are used for controlling respective doubly-fed wind generation sets to carry out reactive compensation according to the doubly-fed wind generation set' s reactive power value distributed by the wind farm power management module. According to the reactive voltage control system of a wind farm of doubly-fed set provided by the invention, the reactive output capability of the doubly-fed wind generation set can be fully developed and cost of reactive-load compensation equipment of the wind farm can be reduced; moreover, an objective of voltage controlling of the wind farm can be achieved by mutual coordination control of the dispatching center equipment, the wind farm power management module and the plurality of blower controllers.