The principle of an illumination system including fly-eyes lenses for a liquid crystal display (LCD) projector with 3-panels was presented and its optical system was designed by using the OSLO (premium edition 6.1) optical system design program. Two panels of the illumination system are well aligned for so that the illumination path length is the same, and the third panel has a longer pass length than the others. The two illumination types with the same or different illumination path lengths were derived by using the paraxial ray design method. Refraction powers and positions of each lens were analytically determined by the method, and the damped least square method was utilized to obtain the optimized uniform illumination system.