A liquid crystal projection system (70) includes a light source (50) for emitting a white light beam of three primary colors, a polarizer (51) for polarizing the white light beam, a separating mirror (52), first and second reflecting mirrors (53, 54), first and second polarization separators (56, 57), a half-wave plate (55), a color separator (58), image modulation devices (60R, 60G, 60B) and a projection lens (59). The separating mirror splits the incident polarized white light beam into two sets of polarized light beams, a monochromatic light beam and a bichromatic light beam that are respectively output to the first and second reflecting mirrors (53, 54). The polarized monochromatic light beam is reflected by the first reflecting mirror, transformed to a light beam with reversed polarization by the half-wave plate, and output to the first polarization separator. The polarized bichromatic light beam is reflected by the second reflecting mirror to the second polarization separator for polarization splitting, and then transmitted to the color separator for separating the two primary colors. The image modulation devices are arranged on sides of the first polarization separator and the color separator for respectively transforming and modulating the incident monochromatic and bichromatic light beams. The projection lens is disposed on one side of the second polarization separator.