A steam generator water level warning method and device are provided. The method comprises: obtaining real-time data of a steam generator water level and a key parameter (S101); detecting whether the key parameter meets a preset key parameter warning condition (S102); if the key parameter meets the key parameter warning condition, receiving an input steam generator water level control instruction by means of an operation interface of a steam generator water level control main interface (S103); performing faster-than-real-time simulation on the steam generator water level by means of a preset faster-than-real-time acceleration mode, the real-time data, and the steam generator water level control instruction, to obtain an operation effect of the steam generator water level in advance (S104); and predetermining, according to the operation effect, effectiveness of the steam generator water level control instruction (S105). The method and device of the present invention predetermine the effectiveness of the steam generator water level control instruction by means of an acceleration function, providing a theoretical basis for an operator to implement a correct operation.