The embodiments of the present disclosure provide an optical assembly and a liquid crystal display device using the optical assembly. The optical assembly has a simple structure and low cost, and can realize a high color gamut display. The optical assembly comprises a first substrate layer, a second substrate layer, and an optical fiber layer arranged between the first substrate layer and the second substrate layer. The optical fiber layer is composed of a plurality of optical fibers arranged closely in a single layer. A plurality of adhesive blocks in contact with the plurality of optical fibers are arranged on a surface of at least one of the first substrate layer and the second substrate layer. At the contact regions between the adhesive blocks and the plurality of optical fibers, total internal reflection in the optical fibers is inhibited by the adhesive blocks.