Return　voltage　method　is　a　nondestructive　testing　technique　for　studying　the　insulation　aging　state　of　power　transformer.　The　return　voltage　contains　abundant　information　about　dielectric　relaxation　response　reflecting　the　insulation　aging　status　of　transformer.　In　order　to　give　full　play　to　the　advantages　of　return　voltage　method　in　diagnosing　transformer　oil　paper　insulation　aging,　a　new　method　is　proposed,　which　evaluates　the　insulation　aging　state　of　transformer　using　the　quantity　of　relaxation　charge.　The　quantitative　relationship　between　the　relative　quantity　of　relaxation　charge　and　the　furfural　content　in　the　transformer　oil　is　given.　First　of　all,　the　return　voltage　curve　is　processed　with　the　time-differential　unfolding　and　the　relaxation　response　function　of　the　return　voltage　is　solved.　Secondly,　the　relative　quantity　of　relaxation　charge　in　the　measurement　process　of　return　voltage　is　calculated　using　the　relationship　between　the　quantity　of　relaxation　charge　and　the　relaxation　response　function.　Finally,　the　relationship　between　the　relative　quantity　of　relaxation　charge　and　insulation　aging　state　is　analyzed.　Analysis　results　show　that　the　quantity　of　relaxation　charge　is　very　sensitive　to　the　aging　of　transformer　oil　paper　insulation.　There　is　a　good　linear　relationship　between　furfural　content　and　the　relative　quantities　of　relaxation　charge　Q1000　and　Q500.　The　relative　quantity　of　relaxation　charge　can　be　used　for　the　quantitative　evaluation　of　the　aging　of　transformer　oil　paper　insulation.　©　2017,　Science　Press.　All　right　reserved.