Abstract: A splicing projection device and method based on a reflective liquid crystal image modulator. In the splicing projection device based on a reflective liquid crystal image modulator, four parallel image lights modulated by first to fourth LCOS chips are formed through optical path designs of one or two light sources, one or two common beam splitting prisms, first to second polarization beam splitting prisms, first to fourth LCOS chips and an imaging lens. A whole image is spliced on a projection plane. The optical path design of the splicing projection device avoids the problem of adding a reflector during the splicing process with respect to the prior art. It can not only realize the parallel image splicing of four chips, but also simplify the optical path structure, and avoid introducing many plane surface errors, and bring great convenience for image splicing adjustment.