A three-dimensional (3D) display system is provided. The 3D display system includes a display device and a switchable grating. The display device is configured to display a set of images with parallax for 3D display. The switchable grating comprises a plurality of switchable grating units, and each switchable grating unit has variable width and variable refractive index and has electric-signal-controllable optical parameters. The switchable grating is coupled with the display device, and configured to enable directional light transmission so as to separate lights of the set of images into predetermined viewing directions to effect the 3D display. Further, the switchable grating includes a first substrate having a plurality of first-type electrodes; a second substrate having at least one second-type electrode; and an optical material contained between the first substrate and the second substrate.