A splicing display system and a display method thereof are provided. The system includes a plurality of display units; a memory configured to store an image signal inputted into the splicing display system; and a controller configured to read each frame of image in the image signal sequentially from the memory through a first transmission interface between the controller and the memory, perform image processing on each frame of image, and transmit a sub-image corresponding to the display unit in each frame of image to each display unit. Each display unit includes a memory module connected with a display screen in the display unit and configured to store the sub-images corresponding to the display unit outputted by the controller. The controller is also configured to control the memory modules to synchronously output the sub-images corresponding to the display units in each frame of image to the display screens.