This paper proposes a novel photonic crystal-based dual-wavelength THz filter.Consisting of a resonator that is the optimized combination of three point defects in a square lattice photonic crystal and line defects

this resonator can realize dualwavelength THz downloading function.It investigates the transmission characteristics of two beams of optical wave in the filter

using the Finite-Difference Time-Domain（FDTD）method

and simulates the corresponding transmission spectrum and time domain response graph.Simulation results show that this filter can perform single-channel dual-wavelength filtering functions and has such advantages as large quality factor Qvalue of a resonator

narrow filtering bandwidth

small loss

fast steady response time

small volume and easy system integration.