In order to solve the curvature measurement problems of flexible mechanism such as biomedical intelligent equipment, software robots and complex structures of high-end equipment, major infrastructure, a highly adaptive curvature sensor was proposed. The fiber Bragg grating was encapsulated in the silicone rubber layer, which was fixed on the polyvinyl chloride matrix to form a flexible silicone rubber curvature sensor based on fiber Bragg grating. The fiber-optic sensor demodulation system and standard curvature calibration blocks were used to measure the characteristics of the FBG sensor′s reflection spectrum and its variation with the calibration block curvature. The relationship between the FBG wavelength shift and the curvature change was analyzed, as well as the sensor sensitivity and the embedded depth of FBG. The experimental results show that the curvature sensor based on silicone-polyvinyl chloride can measure the real-time change of curvature with the highest sensitivity of 0.329 2 nm/m-1. With the increase of the embedded depth of fiber grating, the sensitivity of the sensor gradually increases with the range from 0.2 nm/m-1 to 0.35 nm/m-1. The sensor has good consistency in repeated measurements and can be used for curvature measurement of flexible mechanisms and complex structures.