The invention discloses a grid pulse wave modulation circuit and a modulation method thereof. The grid pulse wave modulation circuit comprises a time sequence controller, a high grid voltage generating unit, a low grid voltage generating unit and a grid driver, wherein the time sequence controller generates an output enabling signal and a plurality of time control signals; the high grid voltage generating unit is electrically connected to the time sequence controller and used for receiving the time control signals and generating a high grid voltage with multi-cutting angle waveform; the low grid voltage generating unit generates a low grid voltage; and the grid driver is electrically connected to the time sequence controller, the high grid voltage generating unit and the low grid voltage generating unit and used for receiving the output enabling signal, the low grid voltage and the high grid voltage with multi-cutting angle waveform and generating a plurality of grid pulse waves according to a plurality of enabling periods of the output enabling signal, wherein each grid pulse wave is grid pulse wave with multi-cutting angle waveform.