Selective　hydrodeoxygenation　of　biomass　and　its　derivatives　to　produce　chemicals　and　biofuels　is　an　effective　upgrading　strategy　to　achieve　global　sustainable　development　goals.　Through　the　development　and　utilization　of　renewable　resources,　sustainable　consumption　and　production　patterns　can　be　promoted　and　climate　change　and　its　impacts　can　be　addressed.　Herein,　selective　hydrodeoxygenation　(HDO)　of　vanillin　was　conducted　by　utilizing　a　Pd/alpha-MoC　catalyst　modified　with　solvent　water.　The　water　modification　induced　the　formation　of　a　thin　layer　of　molybdenum　oxide　on　the　Pd/alpha-MoC　catalyst　surface,　which　significantly　promotes　the　selective　hydrodeoxygenation　of　vanillin.　The　conversion　of　vanillin　over　the　modified　Pd/alpha-MoC　catalyst　reached　99.9　%,　while　the　selectivity　to　4-methyl-2-methoxyphenol　(MMP)　reached　99.9　%　at　0.3　MPa　H2　and　80　degrees　C.　Comprehensive　characterizations　elucidate　that　the　heterogeneous　layer　on　the　surface　of　the　modified　catalyst　significantly　increases　the　acidity　of　the　catalyst　and　improves　the　removal　efficiency　of　hydroxyl　groups,　thus　improving　the　high　selectivity　to　the　desired　product.　Moreover,　the　side　reactions　are　inhibited　due　to　the　using　of　water　as　the　solvent,　which　contributes　a　high　carbon　balance.　The　modified　Pd/alpha-MoC　catalyst　exhibits　efficient　hydrodeoxygenation　of　vanillin　under　mild　conditions,　which　suggests　an　avenue　for　chemical　transformations　of　biomass　derivatives　into　high　value　chemicals.