Owing to its excellent yellow light emission, the (Gd,Y)AG:Ce3+ based phosphors have been widely studied. In this paper, the (Gd,Y)3(Al1-xGax)5O12:Ce3+ (x=0.1-0.8) and (Gd,Y)3(Al1-2yMgySiy)5O12:Ce3+ (y=0.05-0.4) phosphors were successfully prepared by coprecipitation and high temperature solid phase method, respectively. The lattice stabilization, microstructure and fluorescence properties were systematically investigated. With increasing the concentration of Ga3+, the emission peaks of (Gd,Y)3Al5O12:Ga3+/Ce3+ phosphors displayed a blue-shift from ~575 nm (yellow) to ~549 nm (yellow-green), and the decay time was decreased gradually. However, the emission peaks of (Gd,Y)AG:Mg2+/Si4+/Ce3+ phosphors red shifted from ~575 nm (yellow) to ~592 nm (orange-red) with increasing the concentration of Mg2+/Si4+, and the decay time change was similar to the former. The underlying mechanisms were thoroughly investigated and elucidated. In addition, the effect of temperature on the fluorescence properties of (Gd,Y)AG:Ce3+ based phosphors was investigated in detail. The (Gd,Y)AG:Ce3+ based phosphors show promising potential in various lighting and optical display applications.