The invention discloses a system and a method for increasing low voltage ride-through of a wind power generation system through a magnetically-controlled reactor. The magnetically-controlled reactor is serially connected to a connecting line of the wind power generation system and a main grid of a power system; the magnetically-controlled reactor is under control of a control circuit I; the control circuit I acquires a voltage value of a grid-connected bus through a voltage transformer; when the voltage value U3 of the grid-connected bus is normal rated voltage Un, reactance value of the magnetically-controlled reactor is controlled to a minimum value Zmin; when the voltage value U3 of the grid-connected bus ranges from Un to 0.5Un, the reactance value Zmin of the magnetically-controlled reactor is maintained; when the voltage value U3 of the grid-connected bus ranges from 0.5Un to 0, the reactance value of the magnetically-controlled reactor is controlled to range from Zmin to Zmax. Adding a new control target and a new circuit to a control system of a double-fed wind generator is not required; the low voltage ride-through problem of the wind power generation system is solved; the method allows the low voltage ride-through capacity of the wind power generation system to be optimized. The method is simple and reliable.