A dielectric/Ag-coated hollow fiber (HF) temperature sensor based on long-range surface plasmon resonance (LRSPR) is proposed and experimentally demonstrated. The structural parameters, including the dielectric material and layer thicknesses, are optimized through comprehensive theoretical analysis to achieve the best performance. By filling it with a high refractive index (RI) thermosensitive liquid, the GK570/Ag-coated HF temperature sensor with optimal structural parameters is fabricated. Due to the high sensitivity of the LRSPR sensor and the optimized design, the fabricated sensor achieves a temperature sensitivity of 3.6∼20.5 nm/°C, which is almost the highest among the optical fiber temperature sensors based on surface plasmon resonance reported experimentally. Moreover, the detection range of the proposed sensor can be easily tuned up to 170°C by varying the RI of the filled thermosensitive liquid, and the sensor performance remains stable. Considering that most temperature sensors using polydimethylsiloxane have a fixed detection range, this is an outstanding advantage that could expand the application field of the optical fiber temperature sensor.