Abstract: This paper proposes a new structure of periodic photonic crystal based on the hybrid integration of silicon-based waveguides and phase change materials, which is used to construct optical switch device. This device innovatively embeds a one-dimensional photonic crystal structure in a silicon waveguide and fills its nanoscale circular holes with germanium antimony selenide tellurium (Ge-Sb-Se-Te, GSST) phase change material. By regulating the crystalline phase transition of GSST materials, dynamic control of dual-mode optical transmission can be achieved. Theoretical analysis shows that the synergistic effect of silicon waveguides and phase change materials can significantly improve the response speed of silicon-based optoelectronic devices and reduce power consumption. The three-dimensional finite difference time domain (FDTD) method was used to systematically simulate and optimize the optoelectronic characteristics of the device. The results showed that, when GSST is in the crystalline state, the normalized output powers of TE and TM modes are 0.001632 and 0.000820 respectively. The insertion losses are -27.87 dB -30.86 dB respectively. In amorphous state, the insertion loss of both polarization modes can be ignored. This reconfigurable optical switch based on photonic crystal phase change material composite structure provides a new device solution for the next generation of low-power, high-speed optical interconnect systems.