In　ultra-dense　networks,　the　increasing　demand　for　wireless　services　has　led　to　severe　energy　consumption　problem.　In　this　paper,　we　mainly　focus　on　green　communication　and　computation　offloading　in　ultra-dense　networks,　constituted　of　different　macro　base　stations　and　small-cell　base　stations.　This　paper　jointly　considers　edge　energy　consumption　and　delay　under　the　limited　network　resource　for　multiple　users.　To　address　this　issue,　we　propose　an　efficient　computation　offloading　scheme　in　multi-user　multi-task　scenario,　and　a　cuckoo　search　algorithm　is　invoked　for　solving　the　computation　offloading　problem.　To　be　specific,　the　global　convergence　analysis　presents　the　validity　of　this　computation　offloading　scheme.　Finally,　experimental　results　validate　that　our　proposed　scheme　is　conducive　to　improving　the　efficiency　of　entire　system　in　ultra-dense　networks.