A backlight unit, a method for manufacturing the same and a display device are provided. The backlight unit includes a light guide plate, an LED layer and an optical microstructure layer. The light guide plate includes a light incident surface and a light exit surface opposite to the light incident surface. The LED layer is provided on the light incident surface of the light guide plate, and includes plural LED chips arranged in an array. The optical microstructure layer is provided on one of the light incident surface and the light exit surface of the light guide plate, and includes plural optical microstructures in one-to-one correspondence with the plural LED chips. Each of the plural optical microstructures is configured to cause at least a portion of light emitted from a corresponding LED chip to propagate in the light guide plate by total internal reflection.