Coalition　formation　is　a　key　topic　in　multi-agent　systems.　To　solve　the　problem　of　the　number　of　coalition　structure　increasing　rapidly,　OCS　algorithm-formation　of　agent　coalition　structure　based　on　local　optimum　is　given.　Based　on　local　optimum,　the　graph　of　agent　coalition　structure　can　be　shirt　cut　and　the　graph　of　agent　coalition　structure　is　pruned　by　using　the　upper　bound　of　coalition　structures　referred　to　the　partition,　which　decreases　the　searching　space.　Then　it　is　proved　that　the　time　complexity　of　OCS　is　O(3n),　but　experimentally　it　is　already　close　to　0(23n/2).　Finally,　by　contrasting　the　data,　the　efficiency　of　the　OCS　is　indicated.　This　work　can　be　seen　as　the　improvement　of　Rothkopf　and　Liu　Jinglei＇s　related　work.