A synchrotron source offers the advantage of continuous and tunable x rays. Therefore, not only an X-ray nanoprobe can provide the desired spatial resolution to measure the elemental distribution of CaAlSiN3:Eu2+ via X-ray fluorescence mapping but X-ray absorption spectroscopy can also be used to unambiguously analyze the valence states of europium ions (Eu2+ or Eu3+) in different local areas. X-ray excited optical luminescence spectra exhibit only one red emission peak (∼650 nm) corresponding to the 4f65d1 to 4f7 transition of Eu2+, which reveals the fact that Eu2+ ions substitute perfectly for Ca2+ ions at the same site. Through detailed analysis, we demonstrated that the main contribution to the luminescence intensity of CASIN:Eu2+ comes from the Eu2+ activator in the product. We anticipate that X-ray nanoprobes will open new avenues with great characterization ability for studying the emission properties of CASIN:Eu2+.