Abstract: A novel photonic crystal 1×2 splitter is designed based on the self-imaging of multimode interferences in the two-dimensional square photonic crystal waveguides. The transmission characteristics of the splitter is analyzed numerically by the finite-difference time-domain method. In the design process of the photonic crystal waveguide splitter with two out ports, the positions of output waveguides are decided by the positions of the twofold image formed by the self-imaging effect of multimode interferences. The reflective losses are obviously decreased by inserting the dielectric rods, which can vary and match the mode field of the coupling zone, lying at the junctions between the multimode waveguide and single-mode waveguide. The results show that the transmittance of this splitter can be