A series of Si-doped Mg3Y2Ge3O12:Ce3+ phosphors were synthesized by a solid-state reaction method. Mg3Y2Ge3O12:Ce3+ could absorb blue light (400-520 nm) and exhibit a yellow emission band in the wavelength range of 480-750 nm. When 70% Ge in the host lattice is replaced by Si, the crystal field splitting between the two lowest Ce3+ 5d levels is enhanced from 9650 to 11,370 cm(-1), and the bandgap of Mg3Y2Ge3O12 broadens from 5.47 to 5.82 eV. As a result, the emission peak of Mg3Y2Ge3O12:Ce3+ shifts from 573 to 604 nm, which means that the emission color alters from yellow to orange, and the quantum efficiency of the phosphor is enhanced from 4.5 to 54.3%. The enhanced yellow-to-orange emission of Si-doped Mg3Y2Ge3O12:Ce3+ makes it a potential conversion phosphor for warm white light-emitting diodes.