The invention discloses a three-phase load unbalance compensator which comprises a current sampling device, a DSP (digital signal processor) controller, a PI (proportional-integral) controller, a photoelectric coupler and a rectification inversion circuit which are connected sequentially, wherein the current and voltage sampling device comprises four current transformers arranged on an A phase line, a B phase line, a C phase line and a neutral line N respectively; each current transformer is connected with the DSP controller; and the rectification inversion circuit comprises a three-phase four-leg inversion circuit, four inductors and a capacitor. According to the three-phase load unbalance compensator, the three-phase four-leg inversion circuit is applied to the three-phase load unbalance compensator, so that the three-phase load unbalance compensator is high in response speed and precision, can obtain a stable and fast three-phase balance control effect, and realizes comprehensive compensation for reactive power and negative sequence components of a system.