Based on the optical-wave’s theory, focusing energy transmission of UV radiation in rapid prototyping technology has been analyzed in depth. The reflecting focusing theory that continuous spherical wave radiated by point light source is reflected from concave ellipsoidal surface has been enucleated and the axial and lateral optical energy distribution of the reflecting optical wave field has been showed up. The analysis indicates that distribution of the intensity in optical axis is approximately Gauss distribution. And by means of experimentation, the research educes that the UV radiant energy being coupled by optical fiber and being focused by lens is approximately Gauss distribution, too. For effectively utilizing the UV radiant energy and improving the prototyping precision in rapid prototyping, the research supplies sufficient academic basis and has important guidance on the optical design of rapid prototyping.