The　Ru/active　carbon　(AC)　ammonia　synthesis　catalyst　was　prepared　by　the　impregnation　method　using　coconut　(A(BET)　=　1020　m(2)/g)　as　the　support.　Firstly,　AC　was　impregnated　with　RuCl3　aqueous　solution.　Then　the　samples　were　reduced　with　hydrogen,　hydrazine　hydrate　solution　and　hydrazine　hydrate　vapos,　respectively.　Subsequently,　the　three　Ru/AC　samples　were　impregnated　with　aqueous　solution　of　barium　nitrate　and　potassium　hydroxide.　The　Ru　content　was　6%　based　on　the　AC　mass　and　the　molar　ratio　of　Ru:　K:　Ba　was　1:3　:　0.3　in　these　catalysts.　The　catalysts　were　characterized　by　XPS,　N-2　adsorption　and　CO　pulse　chemical　adsorption.　The　results　showed　that　Ru　was　present　in　different　chemical　states　in　the　three　catalysts　obtained　with　different　reductants.　The　catalyst　activity　correlated　with　their　surface　area　and　Ru　dispersion.　The　catalyst　that　was　reduced　with　hydrazine　hydrate　solution　at　pH　=　10　similar　to　13　in　the　range　from　room　temperature　to　90degreesC　for　20　min　had　the　highest　surface　area　of　942　m(2)/g,　Ru　dispersion　of　17.72%　and　catalytic　activity　of　20.36%　(Volume　ratio　of　NH3)　at　low　pressure.　In　this　catalyst　Ru　remained　in　the　metallic　state　when　the　sample　was　exposed　to　atmosphere.