A flat display device includes an array substrate. The array substrate includes a plurality of gate lines, data lines and pixels. The pixels include a plurality of first pixel units and second pixel units, and each of the first pixel units and each of the second pixel units include more than three pixels. The first pixel units and the second pixel units disposed in between two adjacent data lines are arranged alternately, wherein the first pixel units are electrically connected with one of the two adjacent data lines, and the second pixel units are electrically connected with the other data line.