Curvature fiber optic sensors are a kind of novel low cost sensors that can detect curvature directly and distinguish the positive bending and negative bending. This kind of sensor is used to detect torsion deformation of shaft in this paper. The optimal direction of curvature fiber optic sensor was analyzed in osculating plane and rectification plane and maximal sensitivity was gained. The results show that sensor response to the torsion angle is linear approximately. Torsion angle, curvature and bending direction of shaft were measured simultaneously by using curvature fiber optic sensors.