The　Monte　Carlo　method　was　applied　to　simulate　the　microstructural　evolution　of　Al-6Zn-(2Mg)　and　Al-10Zn-1.9Mg-(1.7Cu)　alloys　during　the　initial　ageing　stage,　and　the　effect　of　Mg　and　Cu　was　analyzed.　The　simulation　results　show　that　there　are　Zn　clusters　in　Al-6Zn　alloy　during　the　initial　ageing　stage.　while　in　Al-6Zn-2Mg　alloy,　there　are　distinct　Zn　clusters,　Zn-Mg　clusters　and　a　spot　of　Mg　clusters　in　the　atom　configurations.　The　effect　of　Mg　is　forming　Zn-Mg　short　range　order　structure　by　strong　interaction　of　Mg　and　Zn　atom.　In　Al-10Zn-1.9Mg-1.7Cu　alloy,　there　are　distinct　Zn　clusters,　Zn-Mg　clusters　and　Mg　clusters　in　the　atom　configurations.　Furthermore,　there　are　seldom　Zn-Cu　clusters,　Mg-Cu　clusters　and　Zn-Mg-Cu　clusters.　The　presence　of　Cu　stimulates　the　clustering　of　Zn　and　Zn-Mg,　while　has　no　significant　influence　on　the　clustering　of　Mg　atom.