The invention relates to a method, and an apparatus for accessing to data in response to a power-supply event. The method, performed by a flash controller, includes steps for: repeatedly detecting whether a voltage supplied to the flash controller is lower than a first threshold; and issuing a program command to a flash module for programming data into the flash module and performing a supervision procedure when the voltage is lower than the first threshold. The supervision procedure includes steps for: repeatedly detecting whether the voltage is lower than a second threshold during a time period when issuing the program command to the flash module until transmitting the data to the flash module completely; and cancelling the program command when the voltage is lower than the second threshold.