The　Ba-doped　ZrO2　materials　were　prepared　by　three　methods　and　used　as　support　for　Ru　catalysts　for　ammonia　synthesis,　i.e.,　citric　acid　sol-gel　method　(SG),　modified　co-precipitation　(CP)　and　impregnation　method　(IP).　The　certain　amount　of　analytical-grade　Zr(NO3)(4)center　dot　5H(2)O　and　Ba(NO3)(2)　were　dissolved　in　deionized　water　to　form　a　transparent　mixed　nitrate　solution.　The　citric　acid　was　slowly　added　into　the　mixture　to　form　a　transparent　solution　and　then　heated　to　80　degrees　C　under　vigorous　stirring　until　all　the　water　evaporated　and　a　viscous　material　was　obtained.　After　calcination　at　750　degrees　C　for　5　h　and　a　puffy　white　powder　was　obtained.　This　was　BZ-SG.　The　solution　of　NH3　center　dot　H2O　and　K2C2O4H2O　was　added　dropwise　to　the　mixture　solution　of　Zr(NO3)(4)center　dot　5H(2)O　and　Ba(NO3)(2)　with　vigorous　stirring,　and　the　obtained　white　suspension　was　aged　at　60　degrees　C　for　60　min.　The　resulting　precipitate　was　centrifuged　and　washed　with　distilled　water　for　several　times,　and　then　calcined　at　750　C　for　5　h.　The　obtained　white　solid　was　named　as　BZ-CP.　The　Zr(OH)(4)　was　prepared　by　adding　the　KOH　into　the　Zr(NO3)(4)center　dot　5H(2)O　solution.　Then　the　obtained　Zr(OH)(4)　was　baked　at　300　C　for　3　h　and　impregnated　with　aqueous　solution　of　Ba(NO3)2.　After　dried　at　85　degrees　C　for　12　h,　the　sample　was　heated　at　750　degrees　C　for　5　h　and　obtained　the　BZ-IP　sample.　Ruthenium　catalysts　were　prepared　by　impregnating　the　supports　directly　with　K2RuO4　solution.　After　reduction　with　ethyl　alcohol,　then　was　dried　at　120　degrees　C　for　12　h.　The　samples　with　4　wt%　Ru　were　labeled　as　RBZ-X　(X=　SG　CP　and　IP).　The　molar　ratio　of　Ba　to　Zr　in　all　the　samples　is　1:　9.　The　composites　materials　and　catalysts　were　characterized　by　X-ray　diffraction　(XRD),　temperature　programmed　reduction　of　H-2　(H-2-TPR),　temperature　programmed　desorption　of　CO2　(CO2-TPD),　N-2　adsorption　desorption　isotherms,　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM)　and　CO　chemisorption.　The　results　displayed　that　the　RBZ-SG　catalyst　showed　the　highest　activity　for　ammonia　synthesis　compared　to　those　of　RBZ-CP　and　RBZ-IP.　The　optimum　ammonia　concentration　over　RBZ-SG　catalyst　is　5.72%　under　the　conditions　of　3　MPa,　10000h(-1)　and　425　degrees　C.　This　activity　is　3.8　and　14.3　times　of　that　of　RBZ-CP　and　RBZ-IP,　respectively.　Such　high　activity　is　mainly　resulted　from　the　presence　of　BaZrO3,　which　has　high　electron-donating　ability.　Mobile　electrons　would　be　transferred　from　BaZrO3　to　the　Ru　metal　surface　by　means　of　the　strong　metal-support　interaction　existed　between　Ru　and　reduction　BaZrO3,　which　can　facilitate　the　cleavage　of　N　equivalent　to　N　and　enhance　the　activity　for　ammonia　synthesis　sufficiently.