In this paper, a new structure for an all-optical photonic crystal switch is designed using nonlinear effect. Its structure has been created by using a triangular two-dimensional photonic crystal network of silicon rods in air. In the proposed structure, the coupling of the cavity with the input wave is used for the switching operation. The simulations have been done using finite difference methods in the time domain and expansion of plane waves. Optical switch is a special and generalized mode of optical filter whose output port is turned on or off by the input light power intensity. to be In general, any structure whose performance depends on the intensity of optical power uses an optical switching mechanism. Considering that the basis of operation of all-optical reversible gates in this thesis is also based on the power level of the input signal, therefore it is necessary to deal with optical switching and different switching mechanisms in photonic crystals. . In this article, we try to introduce the optical switch and introduce the most common switching mechanisms.