The invention provides a synchronous display device, and a synchronous tiled display system and a synchronous display method thereof. The technical scheme of the invention is as follows: after the local clock values of the display cards in the tiled display system are obtained, a reference display card is selected according to the local clock values of the display cards, a bit synchronization signal is extracted from the reference display card and is used as the reference input clock signal of the whole tiled display system, thus the display cards in the tiled display system work based on thesame reference input clock signal, then the deviation of the synchronous signals is constant during normal working and is small, thus ensuring the synchronicity of the display signals during tiled display of a plurality of display cards.