Switching is a principle process in digital computers and signal processing systems. The growth of optical signal processing systems, draws particular attention to design of ultra-fast optical switches. In this paper to investigate the operation of the photonic crystal switches, several methods are described. Among different methods, FDTD is a preferable method and is used. We have studied the application of photonic crystal lattices, the physics of optical switching and different types of all optical photonic crystal switches. In this paper, an all optical switch based on photonic crystal directional coupler has been simulated and analyzed by the finite difference time domain (FDTD) method. In this paper, a different structures with changes in central row rods (0.12a) in all optical directional coupler switch have been proposed then electric field intensity and the power output that are two factors to improve the switching performance and the device efficiency, have been  investigated and simulated by using COMSOL software. Manuscript profile