The invention discloses a wind turbine generator set reactive power control method with a force excitation effect, and aims to control a wind turbine generator set which adopts a converter with a force excitation function. The method comprises the following steps: (1) enabling the force excitation function for a main control system of the wind turbine generator set; (2) judging the actual voltage value U of the wind turbine generator set, enabling the force excitation function for the wind turbine generator set, that is, enabling the wind turbine generator set to enter a force excitation mode when U is lower than a low-voltage force excitation operation threshold Ulow or higher than a high-voltage force excitation operation threshold Uhigh, performing lead compensation for force excitation if U is lower than Ulow, performing lag compensation for force excitation if U is higher than Uhigh, and performing compensation according to normal reactive power support when U is between Ulow and a 90% rated voltage of a wind turbine generator set system or between Uhigh and a 110% rated voltage of a wind turbine generator set system. Through adoption of the method, the voltage adaptability of the wind turbine generator set can be enhanced, so that the wind turbine generator set can operate within a wider voltage range, and a stronger support effect on a power grid can be achieved when a system voltage fault occurs; therefore, the method is particularly applicable to a double-fed wind turbine generator set.