The invention provides a reactive power optimization method and device for a wind power plant and the wind power plant. The reactive power optimization method comprises the steps that: the number of control variables in particles is determined according to the states of all wind driven generators in a wind power plant, and the control variables in the particles are reactive power output of the wind driven generators; the number of particles is determined, and the position of each particle is initialized in all the particles; an individual optimal position for each particle is established basedon a pre-established reactive power optimization target function of the wind power plant, and a global optimal position is determined for all the particles; it is determined whether a preset termination condition is satisfied; if the preset termination condition is not met, the position of each particle is updated based on the individual optimal position and the global optimal position, and the individual optimal position and the global optimal position again are determined; and if the preset termination condition is satisfied, the reactive power output of each wind driven generator is controlled in the wind power plant according to the finally determined global optimal position.