Embodiments of the present invention provide a flash memory which has high operating efficiency and a longer service life, and relate to the field of electronic technologies. The flash memory includes a control circuit and a plurality of memory cells, where the memory cell is a floating-gate MOS transistor which includes a source, a gate, a drain, and a substrate; the control circuit is separately connected to the source, the gate, the drain, and the substrate and configured to output a control signal to them, so as to implement a bitwise overwrite operation on the memory cell; and the control circuit is further configured to generate a control signal when data stored by any one of the memory cells is 0, so that the memory cell overwrites the data stored by the memory cell from 0 to 1 according to the control signal.