Traffic　Engineering　(TE)　is　an　efficient　technique　to　balance　network　flows　and　thus　improves　the　performance　of　a　hybrid　Software　Defined　Network　(SDN).　Previous　TE　solutions　mainly　leverage　heuristic　algorithms　to　centrally　optimize　link　weight　setting　or　traffic　splitting　ratios　under　the　static　traffic　demand.　Note　that　as　the　network　scale　becomes　larger　and　network　management　gains　more　complexity,　it　is　notably　that　the　centralized　TE　methods　suffer　from　a　high　computation　overhead　and　a　long　reaction　time　to　optimize　routing　of　flows　when　the　network　traffic　demand　dynamically　fluctuates　or　network　failures　happen.　To　enable　adaptive　and　efficient　routing　in　distributed　TE,　we　propose　a　Multi-agent　Reinforcement　Learning　method　CMRL　that　divides　the　routing　optimization　of　a　large　network　into　multiple　small-scale　routing　decision-making　problems.　To　coordinate　the　multiple　agents　for　achieving　a　global　optimization　goal　in　a　hybrid　SDN　scenario,　we　construct　a　reasonable　virtual　environment　to　meet　different　routing　constraints　brought　by　legacy　routers　and　SDN　switches　for　training　the　routing　agents.　To　train　the　routing　agents　for　determining　the　local　routing　policies　according　to　local　network　observations,　we　introduce　the　difference　reward　assignment　mechanism　for　encouraging　agents　to　cooperatively　take　optimal　routing　action.　Extensive　simulations　conducted　on　the　real　traffic　traces　demonstrate　the　superiority　of　CMRL　in　improving　TE　performance,　especially　when　traffic　demands　change　or　network　failures　happen.　　©　2004-2012　IEEE.