The thermal quenching properties and mechanisms of phosphors employed in white light emitting diodes (wLEDs) are critical for their commercial application. Here, we attempted to characterize the deep traps for capturing and releasing carriers to improve the thermal stability of the blue-emitting CaAl2O4: Eu2+, Tm3+ phosphors. The enhanced thermal stability contributed to the introduction of traps has been demonstrated, and the mechanism of the transport process of carriers, has been explored in detail. In comparison with Eu2+ doped sample, the co-doped Tm3+ samples bring more deep traps. The releasing of carriers in deep traps therefore sustains the luminescence with increasing temperature and compensates the thermal luminescence intensity loss. The results provide a theoretical basis and new field of view for exploring excellent thermal stability phosphors for wLEDs.