We　present　a　new　two-party　quantum　key　agreement　(QKA)　protocol　based　on　Bell　states.　The　participant　transmits　Bell　states　directly　by　inserting　decoy　photons　in　them　randomly.　The　protocol　is　secure　against　the　outsider　attack　and　participant　attack.　Finally,　it　is　generalized　to　multi-party　QKA　based　on　Bell　states.