A temperature and refractive index dual-parameter sensor composed of a cascade of a single-mode fiberBragggrating and a multi-mode Fabry-Perotcavityisproposed. The end of the multi-mode optical fiber is etched with hydrofluoric acid ,and then the depression formed after etching is filled with ultravioletglue to form a Fabry-Perot cavity. The Fabry-Perot cavity and the single-mode fiber Bragg grating are cascaded to form the sensing structure. The Fabry- Perotcavity is sensitive to temperature and refractive index ,while the fiber Bragg grating is sensitive to temperature but not to refractive index. Using the above characteristics ,the sensitivity matrix method can be used to achieve simultaneous measurement of temperature and refractiveindex. Experimentalresultsshow thatthe temperatureand refractiveindex sensitivities of the sensor are - 0. 4832 nm/℃ and - 508. 64 pm/RIU ,respectively. The sensor has the characteristics of a simple manufacturing process ,compact structure ,low cost ,and high sensitivity ,and has good application prospects.