The present invention discloses a display system and a display control method thereof. The display system comprises a display screen, a display controller, and a timing controller. The display controller comprises a 2D to 3D converter for converting image data with 2D format into converted image data with 3D format, and an encoding module for converting the converted image data with 3D format or first image data with 3D format into “2D image plus depth diagram” format data. The timing controller comprises a decoding module for converting the “2D image plus depth diagram” format data into decoded image data with 3D format or scaling the “2D image plus depth diagram” format data into scaled image data with 2D format suitable for outputting on the display screen. Accordingly, the present invention can reduce the required transmission line in order to reduce the production cost.