The present invention relates to a method adopting square voltage waveform for driving a flat lamp used as the light source of a flat panel display or a common light fixture, the method comprising steps of: using a power unit to convert direct current into voltage of square waveform; using a voltage booster to raise the crest of the square voltage waveform to a specific trigger voltage capable of turning on the flat lamp; and providing a pulse-type current while enabling the pulse-type current to be just larger enough to break the dielectric barrier of the flat lamp.