In non-imaging optics, based on the characteristics of the transition of optical extension, the size of elements and beam aperture angles in light pipe illumination optical path of a new type of laser projection display system with the laser diode (LD) array as the light source are given. As an example, the light pipe illumination system design using standard optical design software Zemax is described. The source is 3×8 red LD array. The spatial light modulator (SLM) is a 0.45 inch (1 inch=25.4 mm) liquid crystal on silicon (LCOS). The design includes laser source beam shaping, light pipe uniformity system and the light pipe relay lens. Good performances of energy efficiency and beam uniformity are gotten. Then, the method to design light pipe illumination system with high quality of energy transition in the laser projection display system is shown.