A 1×3 splitter based on self-collimation in a two-dimensional square-lattice photonic crystal is presented. The frequency and the direction of propagation of the self-collimated beams in square-lattice photonic crystal composed of elliptical dielectric rods are obtained by the equal-frequency contours (EFC) which are calculated by plane-wave expansion (PWE) method. Then the elliptical rods are rotated counterclockwise and the EFC is caculated employing PWE method. Based on the above, a 1×3 splitter is realized by photonic crystals composed of elliptical rods with different orientation angles. The transmission characteristics of light in the splitter are analyzed via the finite-difference time-domain (FDTD) method, and the resulting electric fields are also given. It is concluded from the electric fields that a 1×3 beam splitter is realized. The proposed splitter is expected to promote the application of photonic crystals in optical integrated circuits.