Abstract:In this letter,a kind of two-dimensional photonic crystal structure appficable to THz devices is designed,and how to form a microcavity in this structure is discussed.The primary properties of the resonant cavity are analyzed,in which plane wave expansion method is used to make the calculation and the simulation.We've studied the variation of the bandgap structure and resonant frequency in THz region by changing the parameters,such as lattice constant,dielectric constant contrast and idling factor.The research results provided theoretical support for manufacturing the THz devices and the application of THz system.