Diffraction can cause beam divergence. In this study, a new type of waveguide exit port structure was constructed for a photonic crystal by adopting a two-dimensional square-lattice photonic crystal to reduce the divergence and deal with the short radiation distance and low radiation efficiency of the waveguide exit port. First, a Y-shaped channel structure was used for improving the transmittance at the output end; then, multi-branch structures was coupled for improving the convergence of the emitted light to increase the radiation distance of the light wave. Finally, the exit port period was optimized. In addition, analyses and simulations were conducted using the plane wave expansion method and the finite-difference time-domain method. The simulation result denoted that the divergence angle of the emitted light was approximately 3° and that the radiation efficiency exceeded 25% when the radiation distance of the light was 110 μm. Thus, a square-lattice photonic crystal with a Y-shaped defect, 16 exit ports, and 4 exit port periods can achieve well-directed radiation.