We　consider　several　multiset　operations　in　secure　two-party　setting　where　Alice　and　Bob　each　have　a　multiset　and　they　want　to　perform　some　private　computations　over　the　two　multisets　without　revealing　and　private　information　which　means　no　one　of　them　would　learn　more　information　than　what　can　be　deduced　from　the　result.　We　design　some　methods　to　compute　union,　intersection　and　element　reduction　operations　effectively　and　securely　and　apply　these　techniques　to　solve　the　multiset　operations　problems　in　semi-honest　setting　and　consider　their　extension　to　the　malicious　setting.　©　2012　IEEE.