Based on 2-D photonic crystal,a multi-band terahertz (THz) wave filter is pro posed in this paper.Three parallel transverse waveguides are introduced into pho tonic crystal.By changing the radius of some rods and inserting some rods with smaller radius,we can acquire two coupling regions between two adjacent waveguides.The THz wave with specific frequency can be coupled from the middle waveguide to the upside photonic crystal waveguide through the coupling region a nd output from Output1,while the THz wave with another specific frequency can be coupled from the middle waveguide to the downside photonic crystal waveguide through the coupling region and output from Output2.The rest passes through the middle waveg uide directly and is output from Output3.Finally,we can obtain a multi-band THz wave filter.Both the finite-difference time-doma in method and the plane wave expansion method are used to calculate and simulate the performance of the proposed device,which shows that the terahertz waves whose frequences are 3.24THz,3.6THz and 3.75TH z can be output from Output1,Output2and Output3res pectively,whose transfer efficiencies are 95%,98% and 99% respectively.