Employing　the　surface　plasmon　polaritons　(SPPs),　a　kind　of　coupled　metallic　squareness　ring　waveguide　structure　is　presented.　Its　properties　has　been　analyzed　with　the　finite　different　time　domain　method　and　the　coupling　length　has　been　derived　from　the　coupled　mode　theory.　It　is　demonstrated　that　the　SPPs　excited　by　the　light　with　different　wavelength　will　come　out　from　different　output　port　due　to　different　coupling　length.　By　appropriately　designing　the　structure,　it　can　be　utilized　to　realize　some　optics　devices　such　as　multiple-wavelength　sorter　and　beam　splitter.　This　will　break　through　the　diffraction　limit　of　traditional　optical　devices.　(C)　2009　Elsevier　B.V.　All　rights　reserved.