<p>The study of heat and mass transfer in thermal fluids relies on simultaneous temperature and velocity measurement techniques, and temperature-sensitive phosphor-particle-based velocimetry is an effective tool. Among the available methods, the lifetime method performs well in simplicity and precision. However, it faces challenges when capturing the position and phosphorescence intensity of a particle as it moves and decays. A precise phosphorescent-decay particle tracking (PDPT) method based on Gaussian intensity optimization was proposed in this study for phosphorescent particles whose center positions are coupled with the phosphorescence intensity. The PDPT method precisely obtains the center positions and phosphorescence intensities of moving phosphor particles that occupy only a few pixels in a single image, thereby enhancing the accuracy of thermometry and velocimetry. Tests with numerically synthesized particles and experimental measurements were employed to validate the proposed method, which achieved a relative trajectory error of &lt; 0.25% at a particle velocity of 200 pixel/s and a relative temperature error of &lt; 0.05% at 473 K. Compared with existing approaches, the PDPT method showed significant improvements in the tracking ability of the center positions and intensities of individual particles, representing a notable enhancement in the simultaneous temperature and velocity measurement of thermal fluids.</p> Graphical abstract <p></p>