Multi-controller　architecture(flat　or　hierarchical)　has　been　proposed　for　Software　Defined　Networking(SDN).　The　placement　of　these　controllers　is　needed　to　be　considered,　as　which　influences　the　optimization　of　network.　To　optimize　network　by　placing　controllers,　we　develop　our　controller　placement　framework　to　solve　this　issue,　which　is　compatible　for　both　flat　and　hierarchical　control　plane.　Our　algorithm　is　evaluated　at　some　topologies　and　the　simulation　results　show　that:　in　networks　with　varied　traffic,　(1)　load　balance　between　controllers(domains)　is　maintained　well　and　(2)　fewer　inter-domain　flows　are　generated,　which　helps　to　eliminate　the　impact　of　control　state　inconsistency.　©　2015　IEEE.