The invention provides a photovoltaic power-based compensation method for unbalanced load current and reactive power in a power grid. The power grid comprises a grid power supply, a photovoltaic power supply, a load and a controller. The photovoltaic power supply comprises a photovoltaic array. Direct current, generated by the photovoltaic array, is inverted into alternating current through a turn-off element and then transmitted to the grid power supply. The controller is used for compensating the unbalanced load current and the reactive power. According to voltage and current of the photovoltaic array, voltage and current of the load and the current inverted by the turn-off element, the controller adjusts a control angle of the turn-off element. According to the arrangement, the photovoltaic power supply is controlled, the unbalanced load current and the reactive power are compensated, then unbalanced current, loaded into the circuit of the power grid, is improved to achieve the basic balance; and meanwhile, the reactive power is compensated, with power factors increased, and electric energy loss in the circuit is reduced.