Carbon-supported　Ru　catalyst　is　arguably　the　most　promising　applications　of　Ru　catalysts　in　ammonia　synthesis.　However,　the　insufficient　stability　of　Ru/C　catalyst　greatly　limits　its　applications,　and　the　elimination　of　surface　oxygen　species　by　carbon　preactivation　has　been　imagined　to　be　an　efficient　method　for　preparing　Ru/C　catalyst　with　high　stability.　However,　herein　we　demonstrate　that　the　presence　of　some　oxygen　functional　groups　in　carbon　support　of　Ba-promoted　Ru/C　catalyst　was　beneficial　not　only　to　the　dispersion　of　Ru　particles,　but　also　to　the　low-temperature　hydrogen　adsorption.　Furthermore,　the　formation　of　CO　during　heat　treatment,　which　was　closely　related　to　oxygen　groups,　enhanced　the　ammonia　synthesis　activities　of　carbon-supported　Ru　catalyst　with　Ba　promoter.　Therefore,　Ru　catalyst　supported　on　carbon　with　a　large　number　of　surface　oxygen　groups　showed　higher　activity.　Understanding　the　effect　of　carbon　support　surface　on　the　activity　and　stability　of　Ru/C　provides　a　basis　for　the　rational　design　of　the　optimal　carbon-supported　metal　catalyst　for　ammonia　synthesis　and　related　reactions.　©　2018　Elsevier　B.V.