We proposed and experimentally demonstrated a novel high-sensitivity optical fiber temperature sensor (OFTS) which is composed of the Lyot filter cascading a polarization mode interferometer (PMI). The Lyot filter is fabricated by inserting a polarization-maintaining fiber (PMF) between two linear fiber polarizers at two 45-degree angles. By simply cleaving the end fiber of the PMI, the free spectral range (FSR) can be maximized to approach the FSR of the Lyot filter, which introduces the Vernier effect. Experimental results show that the cascaded sensor can provide high-temperature sensitivity of 10.666 nm/°C and 26.562 nm/°C, which are 6.71 and 12.168 times that of single PMI, respectively. The method is demonstrated to achieve a stable and controlled Vernier effect obtaining ultra-high temperature sensitivity, which agrees well with the theoretical simulation results. The proposed sensor has the advantages of high sensitivity, good stability, and easy fabrication.