A light guide plate, a light source assembly, a display panel and a display device are provided. The light guide plate includes a light-emitting surface, a bottom surface opposite to the light-emitting surface and a light-entering surface intersecting with the light-emitting surface and the bottom surface; at least one of the light-emitting surface of the light guide plate and the bottom surface of the light guide plate includes a horizontal portion and an inclined portion protruding out of a plane where the horizontal portion is located along a direction away from both of the light-emitting surface and the bottom surface; the inclined portion is at an end, which is close to the light-entering surface, of the light guide plate, and the inclined portion has an included angle with respect to the horizontal portion.