A light guide assembly and a manufacturing method therefor, a backlight module and a display device. The light guide assembly comprises: a light guide plate (21), the light guide plate (21) having a light emitting surface (212) and a back surface (216) which are opposite to each other, and a side surface (210) connected to the light emitting surface (212) and the back surface (216); a first reflective layer (22), the first reflective layer (22) being provided on the light emitting surface (212) and having a plurality of light transmission holes (221); and a diffusion layer (24) provided on one side of the first reflective layer (22) away from the light guide plate (21), the diffusion layer (24) comprising a plate-like body (241) and a plurality of protrusions (242) provided on the surface of the plate-like body (241), the plurality of protrusions (242) being in one-to-one correspondence with the plurality of light transmission holes (221), and the light transmission holes (221) accommodating the corresponding protrusions (242).