Soft　optical　fiber　curvature　sensor　for　finger　joint　angle　proprioception　was　proposed,　which　was　composed　of　a　protective　silicone　layer,　an　optical　fiber　curvature　sensor　and　two　wearable　fingertips.　The　key　element　of　the　sensor　is　an　in-line　Mach-Zehnder　interference　structure　with　a　seven-core　fiber　and　two　single-mode　fiber　ball.　The　optical　path　difference　between　core　mode　and　surrounding　core　modes　of　the　sensor　could　be　varied　with　the　changes　of　curvature,　which　will　cause　the　shift　of　interference　spectrum.　Experimental　results　show　that　when　the　curvature　change　in　the　range　of　0　similar　to　1　m(-1),　the　curvature　sensitivity　of　the　sensor　was　2.744　nm/m(-1),　and　the　linearity　was　0.9967.　Through　the　verification　test　of　sensing　equipment,　the　based　Mach-Zehnder　interference　soft　optical　fiber　curvature　sensing　approach　is　effective　for　the　measurement　of　the　bending　shape　of　the　joint　angle　model.　The　Mach-Zehnder　interference　sensor　proposed　in　this　paper　has　a　more　compact　structure,　simple　manufacturing　process　and　high　reliability,　which　would　find　potential　applications　in　the　sports　medicine　rehabilitation　or　robotic　monitoring　fields.