This　paper　proposes　an　optical　voltage　transducer　based　on　radial　polarization　demodulation　and　a　four-quadrant　detector　(FQD).　The　voltage　has　been　sensed　linearly　using　an　annular　radial　polarization　grating　to　convert　the　electro-optical　(EO)　phase　delay　into　the　synchronous　rotation　of　a　spot.　The　FQD　is　employed　to　locate　the　spot　to　achieve　voltage　measurement.　Compared　with　the　charge　coupled　device　camera　employed　before　for　the　spot　positioning,　the　measurement　resolution　is　improved　by　nearly　100　times　in　the　range　of　±40°,　the　EO　phase　delay　and　the　measurement　accuracy　is　improved　from　class　0.5　to　class　0.2,　and　the　cost　of　the　image　unit　is　greatly　reduced　by　95%.　©　2019　IOP　Publishing　Ltd.