This paper proposed a fiber sensor based on a Silicon core fiber incorporated with a fused silica grating design. The proposed structure is a nice sensitive in refractive index and temperature variation through theoretical calculation and finite element method simulation. The sensitivities of the refractive index in different polarization directions are 1838.7 and 1949.8 nm/RIU, respectively, within the index range from 1.28 to 1.38 RIU. The temperature range within 15 to 40 oC has the sensitivity up to 1.6 nm/oC by using ethanol analyte. The proposed fiber sensor can provide a method or a solution for intelligent sensing systems.