A high-sensitivity dual-parameter sensor for strain and temperature measurement is developed based on a Sagnac loop cascaded with a fiber Bragg grating (FBG). The sensor employs a misaligned polarization-maintaining fiber (PMF) and few-mode fiber (FMF) structure. The strain and temperature sensing characteristics were systematically analyzed through experiments. The sensor design involves splicing a section of PMF to a single-mode fiber (SMF) with deliberate misalignment along the slow axis, followed by splicing the other end of the PMF to an FMF, creating a misaligned PMF-FMF structure. The ends of this structure were connected to a 3 dB optical fiber coupler, forming a Sagnac loop, which was then cascaded with the FBG to construct the sensing probe. Experimental results demonstrate that the strain sensitivity of the Sagnac loop reaches 19.14 pm/με, with a temperature sensitivity of －1.5 nm/°C. Additionally, the FBG exhibits a strain sensitivity of 1 pm/με, and a temperature sensitivity of 10.8 pm/°C. This sensor achieves high sensitivity for both parameters, enabling simultaneous and accurate measurement of strain and temperature.