The invention provides a slit grating used for a naked eye three-dimensional display device and the naked eye three-dimensional display device. The slit grating comprises a substrate; a plurality of light shielding strips, which are disposed on the substrate at intervals, and are used to shield incident light; wire grids, which are disposed on light-transmitting areas among the light-shielding strips, are used to transmit the first polarization component of the incident light and reflect the second polarization component vertical to the first polarization component of the incident light. The naked eye three-dimensional display device comprises a backlight module group, a liquid crystal panel, and the above mentioned slit grating. The slit grating is disposed between the backlight module group and the liquid crystal panel. Brightness of a display is obviously improved, and at the same time, costs are reduced, and thickness of a product is thinned.