It　is　known　that　uniformly　dispersed　rare　earth　oxide　(RE2O3)　nanoparticles　in　molybdenum　matrix　could　improve　the　ductility　of　Mo.　However,　it　is　reported　that　the　agglomeration　of　La2O3　was　quite　serious　when　the　addition　amount　of　La2O3　was　over　2　wt%,　which　leaded　to　a　dramatic　decrease　of　the　ductility　of　Mo.　In　this　paper,　a　new　type　of　uniformly　dispersed　Er2O3　doped　Mo　powder　was　prepared,　with　the　amount　of　Er2O3　accounting　for　4　wt%.　It　is　found　that　the　reduction　temperature　of　MoO3　was　higher　and　the　grain　size　was　smaller　for　the　Mo　powders　doped　with　Er2O3　than　those　doped　with　La2O3.　First-principles　calculations　illustrate　that　La2O3/Er2O3　had　a　strong　trend　to　be　absorbed　on　the　surface　of　MoO3,　and　the　inhibition　capability　for　the　reduction　of　MoO3　to　MoO2　by　Er3+　was　larger　than　La3+　due　to　the　stronger　Er-O　interactions.　It　gives　a　potential　explanation　of　the　higher　reduction　temperature　of　MoO3　doped　with　Er2O3　than　that　doped　with　La2O3.　Furthermore,　the　formation　energies　of　Er-O　and　La-O　pairs　within　the　bulk　Mo　were　in　the　sequence:　La-O　＞　Er-O　＞　0　eV,　indicating　that　these　systems　are　unstable　and　La2O3　is　easier　to　escape　from　the　interior　of　Mo　grains　and　agglomerate　on　the　Mo　surface　than　Er2O3.　(C)　2019　Elsevier　B.V.　All　rights　reserved.