Luminescence of europium-doped yttrium phosphate (YPO4:Eu) environmental barrier coatings (EBCs) has been developed as a means of self-monitoring. The corrosion behavior of YPO4:Eu in water vapor and molten salt is investigated as well as the effect of these corrosion environments on the intensity of luminescence. By comparison of these results, the relationship between the extent of corrosion of YPO4 and the change in luminescence intensity ratio is determined. Preliminary data suggest that the YPO4:Eu can monitor the microstructural damages including structural perturbations, phase changes and chemical reactions. The results also indicate that the intensity ratio from luminescence spectra can be used as nondestructive evaluation technology for EBCs.