How　to　place　appropriate　controllers　in　different　network　topology　is　a　key　issue　in　software　defined　networks.　Currently,　many　heuristic　algorithms　have　been　proposed　to　provide　an　optimal　solution.　However,　these　heuristic　algorithms　may　be　easy　to　fall　into　local　optimum.　In　this　paper,　a　discrete　cuckoo　search　algorithm　is　applied　to　this　problem.　Experiments　are　conducted　on　two　network　topologies:　OS3E　and　Unicom　backbone　networks.　The　proposed　algorithm　is　compared　with　other　algorithms,　and　simulation　results　show　that　CSA　has　a　best　performance　among　these　algorithms.