Light engine is the core component of LCoS projection system. In order to master the actual work situation of LCoS light engine, and understand the influence of the image quality by practical assemble error,three-chip LCoS light engine of ColorQuadTM structure is chosen as an example, and a method for test image made by LCoS light engine using an optical path system based on optical experimental flatform is introduced. First, the three parts of optical system (the light source module, distribution and composition of light and projec. tion imaging) are built, the result of the experiment is analyzed. Second, in order to make the system has the high quality images, the light road is adjusted and modified by analysis of specific imaging according to the work of each device. Finally, the problems such as uneven brightness distribution, low contrast ratio and double images in the test experiment are summarised and analyzed in detail.