A backlight assembly and a display device are provided. The backlight assembly includes a first sub-optical film including first edge portions and a supporting frame including a first supporting portion which includes rims. The rim includes a first positioning groove and second positioning grooves, the first edge portion includes a first positioning portion in the first positioning groove and second positioning portions in the second positioning grooves; a difference between sizes of the first positioning groove and the first positioning portion is a first space, a difference between a size of each second positioning groove and that of the second positioning portion is a second space greater than the first space; the first edge portions include a first sub-edge portion, the first positioning portion is located at a midpoint of the first sub-edge portion, and the second positioning portions are distributed on both sides of the first positioning portion.