To　achieve　linear　measurement　of　electro-optic　phase　delay　and　improve　the　accuracy　and　measurement　range　of　the　optical　voltage　transducer　(OVT),　this　paper　proposes　a　linear　phase　delay　detection　method　for　an　optical　voltage　transformer　based　on　a　strip　S-wave　plate.　Using　the　strip　S-wave　plate,　the　phase　delay　can　be　directly　converted　into　the　displacement　of　the　dark　stripe　of　the　strip　spot,　and　the　displacement　is　located　by　the　dual-quadrant　detector.　Using　the　Jones　matrix,　we　confirm　the　linear　relationship　between　the　position　of　the　dark　stripe　and　the　phase　delay,　and　propose　a　positioning　method　and　error　compensation　scheme　of　the　dark　stripe　and　set　up　an　experimental　system　to　verify　its　performance.　The　experimental　results　show　that　the　OVT　realizes　the　measurement　of　the　electro-optic　phase　delay;　the　measuring　range　of　the　phase　delay　is　up　to　±40°,　and　the　measurement　error　is　less　than　0.5%.　©　2021　IOP　Publishing　Ltd.