Back plate used for backlight, backlight and display device

The utility model provides a back plate used for a backlight, a backlight and a display device. The back plate comprises a first side and a second side, the first side is provided with a reflecting plane with a first area and a second area, the reflecting plane of the first area and the reflecting plane of the second area are both composed of a plurality of concave arcs, the curvature of the concave arcs of the reflecting plane of the first area gradually increases, the curvature of the concave arcs of the reflecting plane of the second area gradually decreases, and the concave arc with the biggest curvature in the reflecting plane of the first area is connected with the concave arc with the biggest curvature in the reflecting plane of the second area. The light guide plate of the backlight is replaced with the back plate, and the reflecting plane formed by the concave arcs on the back plate is utilized to reflect a light source on a display panel. Due to the fact that the concave arcs have certain curvature, the light emitted by the light source is reflected to be even light rays. The display device utilizes the back plate to replace the light guide plate, and therefore producing cost is greatly reduced.