Spray pyrolysis was applied to prepare Eu2+-doped M3MgSi2O8 (M=Ca, Sr, Ba) phosphor for near-ultraviolet (NUV) light-emitting diode (LED) application. The luminescence characteristics were optimized by a combinatorial screening method combined with spray pyrolysis for the Ca-Sr-Ba ternary system. The first composition library was obtained by measuring the emission spectrum under 395 NUV excitation. In this first screening, the highest luminescence intensity was obtained at (Ca0.9Sr1.2Ba0.9)MgSi2O8:Eu2+, which had 48% enhancement in the integrated emission intensity compared with Sr3MgSi2O8:Eu2+ phosphor. The second screening was conducted for the potential compositions in the first library. As a result, the optimized composition was (Ca0.9Sr0.45Ba1.65)MgSi2O8:Eu2+, which showed 170% enhancement in the integrated emission intensity compared with Sr3MgSi2O8:Eu2+ phosphor.