A　series　of　Ru　based　ammonia　synthesis　catalysts　supported　by　ceria　with　different　promoter　precursors,　such　as　KF,　KNO　3,　Ba(NO　3)　2,　CsNO　3,　were　prepared.　Not　only　studied　the　effect　of　single　and　double　promoters　for　the　catalytic　activity　but　also　studied　the　effect　of　promoters＇　kinds　and　content.　N　2　physisorption,　CO　chemisorption　and　X-ray　diffraction　were　carried　out　to　investigate　the　effect　of　promoter　on　surface　area,　pore　size　distribution　and　ruthenium　dispersion　of　catalysts.　It　has　been　found　that　the　effectiveness　of　F　ion　just　like　the　role　of　alkaline　or　alkaline-earth-promoter　for　ammonia　synthesis.　For　the　single-promoted　Ru/CeO　2　catalyst,　cesium　proved　to　be　most　effective　in　the　studied　four　promoters.　For　the　double-promoted　one,　the　activity　of　the　catalyst　was　affected　remarkably　by　cesium　and　barium　co-exists.　Ammonia　synthesis　concentration　of　over　13.3%　was　obtained　over　Ba+Cs-Ru/CeO　2　catalyst　under　400°C,　10　MPa　and　10000　h　-1.　The　structure　and　the　surface　property　of　Ru/CeO　2　catalyst　were　changed　when　promoters　added.　But　the　real　factor　to　improving　catalytic　activity　is　electronic　effect　rather　than　structural　factors.