Zinc codoping Gd₃Ga₃Al₂O₁₂:Ce (Ce:GAGG) ceramic precursors have been synthesized by chemical co-precipitation method. Thermal gravimetric and differential thermal analysis of the precursor powders are obtained, and phases including GdAlO₃ and GAGG are generated at 883°C. The chemical molecule of precursors is analyzed by FTIR. The phases and morphology of the precursors for different calcination temperature are studied by XRD and SEM. Precursors absolutely convert to Ce:GAGG powders at 900°C. The particles calcined at 1200°C for Ce:GAGG powders with size of 20~60nm become homogeneous and smooth. The effect of PEG on the morphology of the precursors is investigated. Particle size and size range of Ce:GAGG powders calcined at different temperatures were investigated. The influence of codoping of Ce:GAGG with different Zn_²⁺ content on photoluminescence, radioluminescence, excitation spectra and fluorescent lifetime are analyzed. The emission spectra of Ce:GAGG codoping 0.4% Zn_²⁺ content has the highest intensity. The Zn_²⁺ in Ce:GAGG powders has a positive effect on a fast component with short fluorescence lifetime.