Cyclohexanone　is　an　important　raw　material　for　manufacturing　nylon　and　other　chemicals.　The　sustainable　conversion　of　biomass　derived　molecules　to　cyclohexanone　is　desired　but　still　challenging.　Herein,　a　palladium　single　atom　catalyst　anchored　in　the　micropores　of　zeolite　(namely　Pd1/ZSM-5)　is　designed　and　exhibits　remarkable　catalytic　activity　in　transforming　anisole　to　cyclohexanone　in　water　medium　(H2O),　without　using　of　organic　solvent　or　halogen　promoter.　The　selectivity　to　cyclohexanone　is　91.2%　and　the　turnover　rate　(TOR)　is　400.8　h-1　at　453　K.　The　Pd　sites,　acid　sites,　and　microporous　confinement　environment　of　zeolite　cooperate　to　promote　the　partial　hydrogenation　to　cyclohexanone,　and　inhibit　further　hydrogenation　as　the　side　reaction.　H2O　not　only　acts　as　the　solvent,　but　also　participates　significantly　in　the　partial　hydrogenation.　Moreover,　as　revealed　by　isotope　labelled　experiments　(D2O　and　H218O),　the　water　participated　hydrogenolysis　and　the　consequent　partial　hydrogenation　mechanism　is　proposed.