The　rapid　growth　of　IP　traffic　has　contributed　to　the　wide　deployment　of　optical　devices　(ROADM/OXC,　etc.).　Meanwhile,　with　the　emergence　and　application　of　high-performance　network　services　such　as　ultra-high　video　transmission,　people　are　increasingly　becoming　more　and　more　particular　about　the　quality　of　service　(QoS)　of　network.　However,　the　pass-band　shape　of　WSSs　which　is　utilized　in　the　ROADM/OXC　is　not　ideal,　causing　narrowing　of　spectrum.　Spectral　narrowing　can　lead　to　signal　impairment.　Therefore,　guard-bands　need　to　be　inserted　between　adjacent　paths.　In　order　to　minimize　the　bandwidth　waste　due　to　guard　bands,　we　propose　an　effective　distance-adaptation　traffic　dispatching　algorithm　in　IP　over　optical　network　based　on　SDON　architecture.　We　use　virtualization　technology　to　set　up　virtual　resources　direct　links　by　extracting　part　of　the　resources　on　paths　which　meet　certain　specific　constraints.　We　also　assign　different　bandwidth　to　each　IP　request　based　on　path　length.　There　is　no　need　for　guardbands　between　the　adjacent　paths　on　the　virtual　link,　which　can　effectively　reduce　the　number　of　guard-bands　and　save　the　spectrum.