In this paper,we use Z-scan method to test the third-order nonlinear characteristic of GeSbSe chalcogenide glass,and design a photonic crystal optical switching device in co mmunication band based on this matrix material.The photonic crystal switching device is compose d of a photonic crystal microcavity which connects two photonic crystal waveguides in triangular lattice .The plane wave expansion method is used to optimize the bandgap of the photonic crystal structu re.Then the finite difference time domain (FDTD) method is used to analyze the transmission characteristics of the photonic crystal optical switch.Through a series of simulations,adjusting the lattice constant of the photonic crystal switch structure and the point defects radius of the microcavity,and us e the ultrashort pulse laser,a chalcogenide glass ultrafast photonic crystal optical switching can be r ealized,which works at the wavelength of 1550nm.The numerical results show that for 1550nm band communication,by adjusting the pump light intensity at the microcavity,the refractive index will be change d.And it can achieve the light turned on and off.The switch has a lower thres hold power density of 7．7×10⁹W/cm²,high extinction ratio of 25.48dB and high Q-factor of 10 4.