In　the　present　study,　a　series　of　Ru/ZSM-5　catalysts　with　different　pore-size　distributions　were　prepared　and　investigated　for　NH3　synthesis.　Our　studies　indicate　that　Ru/ZSM-5-Mic　with　micropore　structure　exhibits　superior　NH3　synthesis　rate,　which　is　much　higher　than　those　of　Ru/ZSM-5-Mac　(with　macro-　porous　structure)　and　Ru/ZSM-5-Mes　(with　mesoporous　structure)　catalysts.　A　series　of　TPD　experiments　demonstrate　that　pore-size　distributions　play　an　important　role　in　N-2　adsorption　and　activation　over　Ru/ZSM-5.　Moreover,　the　addition　of　La　significantly　promotes　the　NH3　synthesis　performance　over　Ru/ZSM-5-Mic.　Additionally,　in　situ　DRIFTS　studies　indicate　that　the　main　intermediate　species　over　Ru/ZSM-5-　Mic　are　-NH2　,　and　most　of　the　surface　hydrogen　species　desorb　following　the　H2O-formation　pathway.　(C)　2020　Published　by　Elsevier　B.V.　on　behalf　of　Chinese　Society　of　Rare　Earths.