A light source assembly, a backlight module, and a display device are provided in the field of display technology. The light source assembly includes a light source and a collimator. The collimator is arranged on a side of the light source where a light-emergent surface is located. When light emitted from the light source is incident on a preset surface of the collimator, a first included angle is formed between the light and the light-emergent surface. When the light is emitted out of the preset surface, a second included angle is formed between the light and the light-emergent surface. The first included angle is less than the second included angle, and the amount of light incident on per unit area of the preset surface is greater than a preset light amount threshold.