The present disclosure provides a light guide assembly, a fabrication method thereof, a backlight module, and a display device. The light guide assembly includes: a light guide plate having a light exit surface and a back surface opposite to each other, and a side surface contacting the light exit surface and the back surface; a first reflective layer disposed on the light exit surface and having a plurality of light transmissive holes; a diffusion layer disposed on a side of the first reflective layer facing away from the light guide plate. The diffusion layer includes a plate and a plurality of protrusions disposed on the surface of the plate, the plurality of protrusions are in one-to-one correspondence with the plurality of the light transmissive holes, and each light transmissive hole receives a corresponding protrusion.