Return　voltage　measurement　(RVM)　is　being　investigated　for　condition　assessment　of　transformer　insulation,　in　order　to　study　inherent　laws　between　the　mechanism　of　oil-paper　insulation　aging　and　the　characteristics　of　relaxation　response.　A　measurement　platform　is　established　for　RVM　experiments　at　a　constant　temperature　in　the　paper,　and　time-domain　polarization　spectrums　of　return　voltage　are　tested　with　different　water　content,　geometric　conditions　and　aging　conditions.　The　variation　of　oil-paper　insulation　transformer＇s　return　voltage　is　analyzed　by　the　experimental　data　and　dielectric　polarization　response　theory.　The　results　of　experiments　show　that　polarization　spectrums　of　return　voltage　can　be　used　to　diagnostic　the　water　content　of　oil-paper　insulation　transformer　and　aging　conditions;　not　only　the　initial　slope　of　the　charging　time　between　0.01　s　and　10　s　but　also　the　peak　time　of　the　charging　time　between　10　s　and　10000　s　are　important　basis　for　non-destructive　diagnosis;　the　initial　slope　can　directly　reflect　the　aging　degree,　which　is　used　to　distinguish　the　effects　of　moisture　on　the　polarization　spectrums;　dominant　time　constant　which　is　exponential　relationship　with　moisture　content　can　identify　the　condition　of　different　transformer,　it＇s　significant　to　delay　the　transformer　moisture　and　improve　its　operational　reliability.　©,　2015,　Chinese　Machine　Press.　All　right　reserved.