Abstract: This paper proposes a laser temperature sensor based on polarization maintaining fiber (PMF) and few-mode fiber (FMF), and conducted their experimental studies. A 20 cm polarization maintaining fiber was spliced with a 10 cm few-mode fiber and then combined with a 3 dB coupler to form a Sagnac loop, which served as the sensing probe. Light passing through the FMF excites higher-order modes. Due to the diameter mismatch between the FMF and PMF, the higher-order modes are coupled into the stress region of the PMF, exciting the cladding modes and thus improving temperature sensitivity. Experimental results show that after adding the FMF, the temperature sensitivity of the sensor increased from −0.51 nm/℃ to −0.91 nm/℃. This sensor has the advantages of high precision, easy fabrication, and intrinsic safety, making it highly promising for engineering structure safety monitoring applications.