Epoxy/paper　composites　are　main　insulating　component　of　high-voltage　dry-type　bushings.　In　order　to　study　the　effect　of　moisture　on　electrical　properties　of　epoxy/paper　composites,　the　neat　epoxy　resin　and　epoxy/paper　composite　samples　with　or　without　water　were　prepared　by　using　a　vacuum　casting　and　curing　system.　The　water　content　was　controlled　by　mixing　water　with　epoxy　pre-polymer　and　curing　agent　in　a　certain　proportion　during　the　curing　processes.　The　glass　transition　temperature　(Tg),　real　part　of　permittivity　(′),　imaginary　part　of　permittivity　(′′),　space　charge　distribution　and　AC　electrical　breakdown　strength　of　samples　with　or　without　additional　water　were　measured.　The　experimental　results　show　that　the　increase　of　water　content　results　in　the　decrease　of　Tg　and　breakdown　strength　of　the　composites.　Also,　the　′,　′′　and　space　charge　density　increase　with　the　addition　of　water.　The　absorbed　moisture　brings　about　impurities　and　hydroxyl　groups　which　reduces　the　activation　energy　of　polarization,　and　increases　the　trap　density　of　the　sample,　making　it　easier　to　capture　charges,　and　further　affects　the　electrical　properties　of　epoxy/paper　composites.　©　2019　IEEE.