A liquid crystal display device and an array substrate thereof are provided. The array substrate includes: a first data line and a second data line extending along a first direction and being spacedly disposed along a second direction perpendicular to the first direction; a first pixel electrode and a second pixel electrode disposed between the first and the second data lines and spaced from each other along the second direction, the first pixel electrode being disposed adjacent to the first data line, the second pixel electrode being disposed adjacent to the second data line, the first data line being configured for providing a grayscale voltage to the second pixel electrode, the second data line being configured for providing a grayscale voltage to the first pixel electrode. By the above solution, the invention can ensure the display quality of the liquid crystal display device and increase the pixel aperture ratio.