A row (common electrode)-modulation gray-level LCD device and a method thereof, which use a row-modulation device to input at least two sequentially generated original common voltage signals to the common electrode of the same row, whereby the sequentially generated original common voltage signals cooperate with the segment voltage signals to generate voltage differences in the common electrode and turn on or turn off the same monochromatic pixel in a time-division mode. The accumulated effect of the time-division turn-on and turn-off states enables the same monochromatic pixel to present gray-pixel.