A series of quaternary nitride solid solutions with a general formula of Sr1-xCaxLiAl3N4:0.5%Eu2+ was synthesized by a solid-state reaction method. The experimental results showed that a proper amount of Ca-doping can improve the crystallinity and the photoluminescence properties of the produced phosphors. Rietveld refinement showed that the volume of the unit cell shrank with the increase of Ca substitution for Sr, which resulted in a red shift of the emission spectra from 654 to 665 nm under blue excitation at 475 nm. Rietveld refinement and CASTPE calculations suggested that Ca2+ ions prefer to occupy the smaller Sr(I) sites in the crystal lattice, which increases the amount of Eu2+ ions in Sr(II) sites and enables the tuning of the chromaticity coordinates of the obtained phosphors. The thermal stability of the produced phosphors is better than that of commercial Sr2Si5N8:Eu2+ phosphor. The experimental results qualify the solid-solution Sr1-xCaxLiAl3N4:0.5%Eu2+ for consideration as a potential candidate for application in white LEDs.