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Fluorescence intensity ratio (FIR) technique demonstrates significant potential for non-contact temperature sensing with rapid response time, while the design of FIR probes is particularly intriguing. Herein, we report Pr–Al co-doped MgGa 2 O 4 persistent luminescence nanoparticles (PLNPs), as MgAl 0.04 Ga 1.96 O 4 : 0.1 % Pr3+ (MAGP), for ratiometric temperature sensing application. Pr3+ ions function as the emission centers for dual-emission at 612 and 494 nm, while Al3+ ions adjust the lattice environment around Pr3+ ions to enhance the luminescence. Consequently, 274 nm excitation induces the emissions at 494 and 612 nm, as the transitions of Pr3+ for 3P 0 →3H 4 and 1D 2 →3H 4 , respectively. The emission mechanism is substantiated by density functional theory calculations, regarding the electronic transitions of Pr3+. Ratiometric temperature sensing is achieved over the temperature range of 303–573 K with the thermally non-coupled mechanism of the 3P 0 /1D 2 energy levels by FIR at 612 and 494 nm, respectively. The maximum relative sensitivity was 0.91 %. The mechanism is corroborated as the non-thermally coupled energy levels through intervalence charge transfer. Thus, the reversible and sensitive response was illustrated for temperature measurement and the non-thermally coupled mechanism is efficient for the design of ratiometric temperature sensors. Ratiometric temperature sensing was utilizing the 3P 0 /1D 2 non-thermal coupled level of Pr–Al co-doped MgGa 2 O 4. When the temperature changes, the emissions at 494 and 612 nm varied differently to realize FIR thermometry with a strong nonlinear correlation. [Display omitted] • Pr–Al co-doped MgGa 2 O 4 persistent luminescence nanoparticles was prepared by co-precipitation method. • The luminescence properties and mechanism of the prepared sample MAGP were analyzed under 274 nm excitation. • The emission was confirmed to be attributed to the electron jump of Pr3+ by density functional theory. • The intervalence charge transfer theory to explain the mechanism of temperature sensing in the 3P 0 /1D 2. [ABSTRACT FROM AUTHOR]