<p>Single-core dual-parameter sensors have wide applicability and importance in the fields of environmental monitoring, smart home, and medical health. In this paper, a single-core photonic crystal fiber (PCF)-surface plasmon resonance (SPR) sensor based on Tantalum pentoxide (Ta₂O₅) modulated thermometry layer is proposed for the efficient measurement of refractive index (RI) and temperature (<i>T</i>) in the meantime. The structure of the sensor is the upper and lower polishing type, and the polishing depth is the same. The upper polished surface is covered with gold film for measuring RI, and the lower polished surface is covered with Au + Ta₂O₅ + polydimethylsiloxane (PDMS) for measuring <i>T</i>. The single-core design can effectively reduce crosstalk problems. The addition of Ta₂O₅ film in the thermometry layer can adjust the formant to the near-infrared region, thus expanding the measuring range of RI or <i>T</i>. The high RI of Ta₂O₅ also makes the surface plasmon resonance more significant and can effectively enhance the electric field in the fiber, thus improving the sensitivity of <i>T</i> sensing. Finally, the RI sensitivity of 9600&#xa0;nm/RIU (RI range of 1.33 ~ 1.41) and the <i>T</i> sensitivity of 15.2&#xa0;nm/°C (<i>T</i> range of 0 ~ 40&#xa0;°C) are obtained by the finite element method. Dual-channel sensing of RI and <i>T</i> is achieved within a single core, effectively eliminating crosstalk. The sensor proposed in this paper has the advantages of high sensitivity, wide detection range, strong anti-interference, simple structure, and easy manufacturing and is a strong competitor in the field of <i>T</i> and RI measurement at the same time.</p>