A light guiding system includes an ambient light gathering system, multiple light guiding devices and a wedge light guiding bar. The ambient light gathering system facing ambient light is used for absorbing the ambient light. Each light guiding device absorbs the absorbed light. The wedge light guiding bar has a light-out surface and a light-in surface coupled to the light-out surface. The light-in surface is a wide surface coupled to an inclined surface. The light-out surface is opposite to the inclined surface and next to a light-in side of a light guide plate. The wedge light guiding bar for use in the light guiding system, an edge-lighting backlight module and an LCD device can reduce cost of material and weight. Also, the light uniformity of the light output end is improved and the optical quality of the edge-lighting backlight module is raised.