A　new　optical　voltage　sensor　based　on　radial　polarization　detection　is　proposed　in　this　paper,　and　then　the　linear　and　direct　measurement　of　an　electro-optic　(EO)　phase　delay　can　be　realized.　The　sensor　mainly　consists　of　an　EO　crystal,　a　quarter-wave　plate,　a　newly　designed　radially　polarized　grating,　and　an　image　collecting　system.　The　quarter-wave　plate　is　employed　to　convert　the　EO　phase　delay　to　a　rotation　of　the　polarization　plane　of　a　linearly　polarized　light,　and　then　the　grating　is　to　convert　it　into　the　rotation　of　a　ring　facular,　so　the　EO　phase　delay　can　be　measured　directly　by　positioning　the　dark　stripe　center　in　the　facular.　The　principle　of　the　sensor　is　analyzed　by　Jones　matrix.　The　experimental　results　show　that　this　new　sensor　can　achieve　a　good　linear　measurement　of　the　EO　phase　delay　in　the　range　of　360　degrees　with　the　measurement　error　less　than　0.5%,　and　has　no　limits　of　the　half-wave　voltage　of　crystal.