The invention discloses a reactive power control method and system for a wind power plant. The method comprises: an AVC (Automatic Voltage Control) substation acquiring target reactive power of the wind power plant, and sending a reactive power adjusting instruction to reactive power compensation equipment according to the target reactive power; the reactive power compensation equipment performing reactive power compensation according to the working mode thereof; and after detecting that the reactive power of the wind power plant reaches the target reactive power, the AVC substation controlling a wind turbine generator in the wind power plant to increase reactive power, so as to replace the reactive power output of the reactive power compensation equipment. The wind turbine generator and the reactive power compensation equipment coordinate to allocate and control the reactive power, and the reactive power compensation equipment is adjusted to preferentially act by sufficiently utilizing and coordinating the reactive power capability of the wind power plant so as to quickly meet the response requirement; and after the voltage of a grid-connected point is stable, the reactive power of the wind turbine generator is increased to replace the reactive power output of the reactive power compensation equipment, thereby providing more surplus capacity for the reactive power compensation equipment and quickly following next reactive power control.