Ruthenium-based　catalysts　are　widely　used　in　ammonia　(NH3)　synthesis　because　of　a　high　affinity　for　N2　activation,　while　confronting　the　challenge　of　facile　deactivation　due　to　sintering.　Herein,　for　the　first　time,　we　develop　a　highly　active　and　sintering-resistant　Ru2.1-CC　catalyst　via　colloid　carbonization　(CC)　for　NH3　synthesis.　It　exhibits　a　superior　NH3　synthesis　rate　around　9.4-fold　that　of　Ru　catalyst　synthesized　by　impregnation　method,　displaying　extremely　high　stability　without　aggregation　of　Ru　nanoparticle　after　100　h　stability　test.　Our　studies　show　that　Ru2.1-CC　possesses　the　average　Ru　particle　size　of　2.1　nm　with　narrow　size　distribution　and　thus　exposes　more　active　sites　for　N2　activation.　Moreover,　the　formation　of　Ru-C　interaction　via　colloid　carbonization　over　Ru2.1-CC　can　stabilize　Ru　particle　size　to　realize　high　stability,　meanwhile　reduce　work　function　and　upshift　the　d-band　center　of　Ru　metal　to　accelerate　its　electron　transfer　for　N2　activation　and　NH3　synthesis.　This　study　provides　a　new　strategy　for　simple　synthesis　of　noble　metal-based　catalysts　that　are　highly　active　and　stable　for　NH3　synthesis.　©　2023　Elsevier　Ltd