High-performance　THz　band-pass　filters　are　highly　demanded　for　THz　spectroscopy　and　imaging　applications.　In　this　work,　we　have　analyzed　the　spectral　features　of　a　THz　band-pass　filter　and　divided　the　spectrum　into　three　spectral　regions,　including　a　pure　waveguide　region,　a　subwavelength　region　and　a　cut-off　region.　Based　on　the　understanding　of　the　spectrum,　we　have　proposed　and　fabricated　two　kinds　of　THz　band-pass　filters,　which　were　characterized　by　timedomain　THz　spectroscopy　and　show　narrow　bandwidths　and　high　stopband　suppression.