Solid solution phosphors Gd3Ga2(Al3-ySiy)(O12-yNy):Ce3+ were synthesized by introducing [Si4+ + N3-]/[Al3+ + O2-] co-substitution into the lattice of Gd3Ga2Al3O12:Ce3+center dot Gd3Ga2Al3O12:Ce3+, characteristic as outstanding light yield (about 50-60 kPh/MeV), and has been applied in computer tomography (CT), positron emission tomography (PET) nuclear medical detector, et al. With the increase of y value, the coordination environment around Gd3+(Ce3+) shrinked, which were confirmed by combining techniques of structure refinement, energy-dispersive spectrum, elements distribution mapping. As a result, stronger 5d orbital nephelauxetic effect (epsilon(c)) and bigger 5d energy level splitting (epsilon(cfs)) were induced. Thus resulting in longer wavelength of excitation and emission from Ce3+, and broadening of emission spectra. The typical sample Gd2.95Ga2Al2.5Si0.5O11.5N0.5:0.05Ce(3+) (GGASON(0.5):Ce3+) exhibits sufficient red component and persistent luminescence(> 10 ms), enables fabrication of warm white light suited for alternating-current (AC) when combined with blue light chip (460 nm).