Ammonia　has　been　considered　as　a　promising　hydrogen　carrier　with　high　energy　storage　density　and　easy　transport.　Here,　we　report　the　ruthenium　(Ru)　nanoparticles　supported　on　LaAlO3,　a　typical　ABO3　perovskite　oxide,　as　an　efficient　catalyst　for　ammonia　decomposition.　By　tailoring　the　cation　substitution　of　La3+　by　Sr2+,　the　electronic　properties　of　support　materials　were　modulated,　which　exerts　an　impact　on　the　electronic　state　of　Ru　active　sites.　It　is　found　that　the　Ru/La0.8Sr0.2AlO3　catalyst　has　a　high　hydrogen　formation　rate　and　low　activation　energy.　In　situ　spectroscopic　investigation　and　NH3　temperature　programmed　desorption　(NH3-TPD)　analyses　indicate　the　electron-rich　state　of　metallic　Ru　on　the　La0.8Sr0.2AlO3　support,　which　promotes　associative　desorption　of　N　atoms　and　accelerates　NH3　decomposition　reactions.　This　study　provides　a　universal　strategy　of　aliovalent　cation　substitution　to　engineer　the　electronic　properties　of　metal/oxide　catalysts　as　well　as　their　catalytic　activities.　©　2022　Elsevier　Ltd