Ammonia　(NH3)　is　an　excellent　candidate　for　hydrogen　storage　and　transport.　However,　producing　NH3　under　mild　conditions　is　a　long-term,　arduous　task.　Atomic　cluster　catalysts　(ACCs)　have　been　shown　to　be　effective　for　catalytic　N2-to-NH3　conversion,　opening　the　door　to　the　development　of　efficient　catalysts　under　mild　conditions.　Still,　ACC　formation　with　thermally　stable　catalytic　sites　remains　a　challenge　because　of　their　high　surface　free　energy.　Herein,　we　report　anchoring　Ba　and/or　Ce　onto　Ru　ACCs　(2　wt%　Ru　atomic　clusters　supported　on　N-doped　carbon)　to　form　so-called　clusters-metal　oxide　promoters　electronic　interaction　(CMEI)　to　stabilize　the　Ru　atomic　clusters.　The　resulting　Ba/Ce/Ru　ACCs　significantly　boost　the　NH3　synthesis　rate　to　56.2　mmolNH3　gcat-1　h-1　at　400　degrees　C　and　1　MPa,　which　is　7.5-fold　higher　than　that　of　Ru　ACC.　The　strengthened　CMEI　between　the　Ba/Ce　and　Ru　atomic　clusters　across　the　Ba/Ce/Ru　ACC　enables　electron　transfer　from　Ba　and/or　Ce　to　Ru　atomic　clusters.　As　such,　the　electron-enriched　Ru　atom　could　facilitate　electron　transfer　to　N　equivalent　to　N　bond　pi*　orbitals,　which　would　weaken　the　N　equivalent　to　N　bond　and　drive　the　eventual　conversion　of　N2　to　NH3.　This　study　offers　insight　into　the　role　of　CMEI　in　Ru　ACCs　and　provides　an　effective　approach　for　designing　stable　atomic　cluster　catalysts　for　NH3　synthesis.