Co-stabilization　of　multiple　precipitates　has　attracted　growing　attention　as　a　promising　approach　to　improve　the　performance　of　Al-based　alloys　at　elevated　temperatures.　In　this　paper,　three　microalloying　strategies,　including　0.18　at.%　Sc,　0.18　at.%　Sc　with　0.05　at.%　Si,　and　0.18　at.%　Sc　with　0.05　at.%　Zr,　are　adopted　to　acquire　an　assembly　of　theta＇-Al2Cu　and　Al3Sc　precipitates　in　Al-1.08　at.%Cu　alloys.　The　differences　in　chemical　compositions　are　found　to　have　huge　impact　on　the　stability　of　the　precipitates　and　thus　on　the　softening　resistance　of　the　alloys　during　thermal　exposure　at　300　degrees　C.　The　results　show　that　compared　with　Sc　or　Sc-Si　microalloying,　Sc-Zr　microalloying　in　Al-Cu　alloy　is　far　more　effective　to　co-stabilize　the　dual　precipitates　and　thus　improve　the　high-temperature　resistance.　Using　transmission　electron　microscopy　(TEM),　the　underlying　mechanisms　responsible　for　the　distinct　microalloying　effects　of　the　three　strategies　are　revealed　by:　(i)　the　limited　improvement　of　high-temperature　resistance　in　Sc-Si　microalloyed　Al-Cu　alloy　results　from　a　cumulative　effect　of　the　retarded　theta＇-Al2Cu　coarsening　and　the　accelerated　Al3Sc　growth.　(ii).　the　combined　Sc-Zr　microalloying　simultaneously　stabilizes　theta＇-Al2Cu　and　Al3Sc　precipitates,　which　dramatically　suppresses　the　softening　in　Sc-Zr　microalloyed　alloy.　Further　experimental　evidences　of　atom　probe　tomography　(APT)　suggest　that　the　theta＇-Al2Cu　stabilization　induced　by　combined　Sc-Zr　or　Sc-Si　microalloying　is　actually　related　to　a　modified　multiple　solute　segregation　at　theta＇-Al2Cu/alpha-Al　interface　to　reduce　the　interfacial　free　energy.　And　the　suppression　and　acceleration　of　Al3Sc　coarsening　kinetics　induced　by　Sc-Zr　and　Sc-Si　microalloying　are　attributed　to　Si-accelerated　Sc　diffusion　and　the　formation　of　core-shell　structural　precipitates,　respectively.　(C)　2020　Elsevier　B.V.　All　rights　reserved.