Abstract Micro-injection molding is the most important technology in optical MEMS/NEMS industry for the necessary of scale, velocity and cost by the development of optical MEMS/NEMS industry and the innovation of optical MEMS/NEMS industry. It has the advantage of low cost, low interface and small volume in optical MEMS/NEMS industry. This paper emphasizes the analysis for light guiding plate of liquid crystal display on micro-injection molding. The finite element simulation in a three-dimensional inertia-free, incompressible flow is presented. A control volume scheme with a fixed finite element mesh is employed to predict melt front advancement. The plastic material of light guiding plate is used for PMMA material. The results show that the short shot situation on the filling stage of micro-injection molding. The results also indicate that the processing is very well for micro-injection molding by numerical simulation.