Mg3Sb2-based　alloys　are　promising　thermoelectric　materials　through　n-type　doping　in　Mg-rich　growth　conditions　to　overcome　their　intrinsic　p-type　behavior.　First　principle　calculations　are　employed　to　investigate　the　dopant　formation　energy　and　electronic　structures　of　Y-doped　Mg3Sb2.　Results　indicate　that　the　Y　atom　is　more　favorable　for　substitution　at　the　cation　site.　Simultaneously,　the　flattened　band　structure　and　increased　density　of　state　near　the　Fermi　level　of　Y-doped　Mg3Sb2　indicate　an　enhanced　electronic　transport　performance.　The　carrier　concentration　rises　to　5.31　x　10(19)　cm(-3)　at　room　temperature,　resulting　in　a　significant　increased　power　factor　for　Mg3.17Y0.03Sb2.　The　available　optimization　of　electrical　transport　contributes　to　excellent　thermoelectric　performance,　and　a　peak　ZT　similar　to　0.83　at　773　K　was　achieved　for　Y　concentration　x　=　0.03　in　Mg3.2-xYxSb2.　This　work　provides　an　alternative　measure　for　optimizing　the　thermoelectric　performance　of　n-type　Mg3Sb2　alloys　by　cation　site　doping.　(c)　2019　The　Chinese　Ceramic　Society.　Production　and　hosting　by　Elsevier　B.V.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).