A novel red-emitting phosphor CaSrAl 2 SiO 7 :Eu 3+ was firstly synthesized through the high temperature solid state reaction at 1300°C. The structure, diffuse reflection spectra, photoluminescence spectra, color-coordinate parameters and quantum efficiencies (QE) of phosphors were investigated. The obtained CaSrAl 2 SiO 7 :Eu 3+ phosphors have the same structure with that of the Ca 2 Al 2 SiO 7 and Sr 2 Al 2 SiO 7 phosphor, which have the melilite structure. Optical properties were studied as a function of Eu 3+ concentration x, when x>0.14, the intensity of absorption of the f–f transitions of Eu 3+ at 393nm is stronger than that of the broad charge transfer transition band (CTB) around 254nm, and which matches well with the output lights of NUV–LEDs, whereas, the concentration of Eu 3+ x≤0.14, the absorption of 393nm is weaker than that of CTB. The underlying reason of Eu 3+ concentration on their luminescent properties was investigated and discussed in detail. As a result, comparing with the commercial red phosphor Y 2 O 2 S:Eu 3+ , the CaSrAl 2 SiO 7 :xEu 3+ (x>0.14) phosphor exhibited excellent color purity and much higher brightness and could be considered as promising red phosphors for NUV–LEDs.