The　measurement　results　of　the　optical　voltage　transducer　based　on　the　nonlinear　demodulation　mode　are　related　to　the　optical　power,　and　the　half-wave　voltage　limits　its　voltage　measurement　range.　To　solve　the　above　problems,　this　paper　proposes　a　linear　optical　voltage　transformer　based　on　Newton　ring　sub-wavelength　grating.　Compared　with　the　radial　analyzer　grating,　the　extinction　ratio　of　the　Newton　ring　grating　is　evenly　distributed　in　the　radial　direction.　It　converts　the　electro-optic　phase　delay　into　the　synchronous　rotation　of　the　spot　image.　The　four-quadrant　detector　is　used　to　locate　the　spot　image　for　real-time　linear　measurement　of　the　voltage　signal.　The　experimental　results　show　that　the　measurement　result　of　the　optical　voltage　transformer　is　independent　on　the　optical　power,　and　the　measurement　range　of　the　electro-optic　phase　delay　can　reach　±80°,　and　the　accuracy　level　is　0.2　in　laboratory　conditions.　©　2020　Automation　of　Electric　Power　Systems　Press.