A display with dimension switchable function is introduced herein. The display can selectively display 3D images or 2D images in a part of or entire of a display area of display. The display at least includes a collimated backlight module, an image display device, a light guiding module, and a switching unit. The light guiding module and the switching unit are disposed between the collimated backlight module and the image display module, and positions thereof can be exchanged according to different design requirements. The light from the collimated backlight module is directed to different viewing zones after passing through the light guiding module. By controlling diffusion states of the switching unit, the 3D images or the 2D images are selectively displayed in a part of or entire of the display area of the image display module, as required.