This　paper　presents　a　novel　optical　current　transducer　based　on　Newton＇s　ring　sub-wavelength　grating.　It　converts　the　Faraday　rotation　angle　into　synchronized　rotation　of　the　spot　image　and　locates　the　spot　with　a　four-quadrant　detector　to　achieve　real-time　linear　measurement　of　the　current.　The　Newton＇s　ring　grating　is　used　instead　of　a　radial　grating　as　a　polarization　detection　device　so　the　extinction　ratio　is　distributed　uniformly　in　the　radial　directions　and　the　polarization　characteristics　have　no　change　with　the　radial　direction,　thereby　a　higher　measurement　accuracy　has　been　achieved.　The　angle　measurement　range　can　reach　+/-　40　degrees　which　breaks　through　the　limitations　of　the　intensity　demodulation　mode.　The　performance　of　the　transducer　has　been　verified　by　experiments　and　a　0.2　S　class　accuracy　achieved　with　a　linear　measurement,　no　interference　of　optical　power　fluctuation,　and　minimized　the　effect　of　birefringence.