In this work, a series of ZnAl(1.99-x)GaxO4:0.5%Cr3+ (x = 0, 0.1, 0.3, 0.5, and 0.7) phosphor powders were prepared by a solid-phase reaction. As the Ga3+ doping concentration increased, the crystal field strength Dq/B gradually decreased from 2.778 to 2.648, indicating a progressive weakening of the octahedral field strength. In result, red shift and spectral broadening have been observed in the photoluminescence excitation (PLE) and photoluminescence (PL) spectra of the Ga3+ substituted samples. Compared with ZnAl1.99O4:0.5%Cr3+, the PL spectrum of ZnAl1.49Ga0.5O4:0.5%Cr3+ was wider and the full width at half maximum (FWHM) was increased from 23.2 nm to 31.8 nm. And the PL intensity was increased by 1.8 times. Due to Ga3+ incorporation into the ZnAl2O4 lattice, the [AlO6] octahedron was expanded, which provides a more suitable coordination environment for Cr3+, and the PL thermal stability was increased from 65% to 70% at 150 °C. These results show that appropriate replacement of Al3+ by Ga3+ effectively improves the PL performance of ZnAl1.99O4:0.5%Cr3+ red phosphor and makes up the red component deficiency of pc-WLEDs singly based on the YAG:Ce3+ phosphor.