Combining　molecular　dynamic　(MD)　simulation　with　modified　analytic　embedded-atom　method　(MAEAM)　potential,　the　formation,　migration　and　activation　energies　have　been　calculated　for　four-kind　migrations　of　Cu　vacancy　and　three-kind　migrations　of　Ag　vacancy　in　Cu-Ag　immiscible　alloy　system.　The　equilibrium　concentration　of　Cu　vacancies　is　greater　than　that　of　Ag　vacancies　owing　to　the　formation　energy　of　Cu　vacancy　(1.012　eV)　is　lower　than　that　of　Ag　vacancy　(1.169　eV).　Comparing　the　migration　or　activation　energy　needed　for　four-kind　migrations　of　Cu　vacancy　and　three-kind　migrations　of　Ag　vacancy　show　that　the　favorable　migration　mechanism　is　the　nearest-neighbor　(NN)　jump　for　Cu　vacancy,　while　the　straight　[010]　six-jump　cycle　(6JC)　for　Ag　vacancy.　Furthermore,　the　activation　energy　of　the　NN　jump　of　Cu　vacancy　(2.164　eV)　is　lower　than　that　of　straight　[010]　6JC　of　Ag　vacancy　(2.404　eV)　also　show　that　the　former　is　more　favorable.　We　conclude　accordingly　that　the　primary　migration　mechanism　is　the　NN　jump　of　an　abundance　of　Cu　vacancies.　(c)　2006　Elsevier　B.V.　All　rights　reserved.