The invention discloses a prism diaphragm, a curved backlight source and a display device. The prism diaphragm comprises a base, and a plurality of triple prism units which are arranged in an array form on the base; each triple prism unit is equipped with a triangular cross section which is equipped with a first base angle and a second base angle, wherein the first base angle and the second base angle are both located at one side of the cross section, close to the base; the first base angle and the second base angle of the triangular cross section of at least one of the plurality of prism units are different. By adopting the prism diaphragm, the curved backlight source and the display device, the uniformity of brightness of the emergent light can be improved, the visual angle is increased, and as a result, the visual effect is improved.