A new kind of prism light guide is introduced in this paper. The guide is seamless and made by extruding technique, which makes it has lower cost. The cost of the guide is only about 15% of the price of prism films. The guide transport light by total internal reflection and the light-transporting principle is described in detail in this paper. In theory all light would be transported by the process of total internal reflection but irregularities in the guide cause a small proportion of light to leak out the guide. This effect can make the guide glow and for this reason the seamless prism light guide acts as both a light transport and emission device. The guide can be used in lighting or daylighting of underground buildings and windowless buildings, or buildings in which inflammable and explosive products are manufactured. It can also be used in nightscape lighting as a decorative lighting fixture. In this paper, the application of the guide in a concrete-curing room is introduced briefly.