Abstract: The flat 3D display technology is a novel virtual reality technology, in which people can see 3D stereoscopic images from a screen directly and do not require any device to be worn. To promote the development of the flat 3D display technology, this paper introduces the imaging principle of parallax pictures and some flat 3D display methods including barrier 3D displays, microlens 3D displays, polarizer 3D displays, multiview lenticular stereoscopic displays and so on. Then, it analyzes on the advantages and disadvantages about these methods. By taking the fourview autostereoscopic displays from Sanyo in Japan, multiview 3D displays from Nanjing University and the Horizontally Doubledensity Pixels(HDDPs) 3D displays in NEC for examples, it introduces the recent research and potential development, describes technique problems, and forecasts the application prospects for the flat 3D display technology.