Noble　metal　decoration　is　one　of　the　most　efficient　strategies　to　boost　the　performance　for　water　oxidation.　However,　identifying　the　role　of　noble　metals　and　especially　the　active　sites　remain　a　persistent　challenge.　Here,　we　report　a　direct　synthesis　of　Au　nanoparticles　(NPs)　decorated　NiFe　oxyhydroxides　via　in-situ　electrochemical　conversion　and　a　comprehensive　study　of　the　activity　boost　via　a　combination　of　systematic　experimental　and　theoretical　studies.　We　found　that　Fe　doping　greatly　improved　the　electrical　conductivity　and　the　Fe　sites　were　the　dominant　active　centers,　collectively　responsible　for　the　remarkably　enhanced　performance　in　NiFe　oxyhydroxide.　Upon　Au　NPs　decoration,　the　content　of　high-valence　Fe/Ni　ions　was　substantially　reduced　and　the　formation　of　surface　oxygen　vacancy　was　greatly　suppressed.　As　a　result,　the　dominant　active　centers　transfer　to　the　interfacial　Au　sites　that　directly　participate　in　catalyzing　water　oxidation.　Our　study　presents　a　fundamental　insight　into　the　origin　of　activity　enhancement　and　especially　the　active　centers　in　noble　metal　decorated　NiFe　oxyhydroxide　catalysts.