A series of europium-ion doped CaLa4Si3O13 phosphors were synthesized by using a conventional high-temperature solid-state method. X-ray powder diffraction patterns and photoluminescence spectra were utilized to characterize the as-prepared phosphors. The phosphors show tunable luminescence owing to the existence of Eu2+ and Eu3+ emission. A typical emission maximum of Eu2+ is about 460 nm, and Eu3+ shows a predominant 5D0-7F2 transition emission. The emission of Eu2+ shifts toward the long wavelength side with increasing doping concentration. The site occupancy of Eu2+ and Eu3+ is analyzed according to their luminescence behaviors. The Eu3+ ion at the Ca2+ site can be partially reduced to Eu2+, but at the La3+ site cannot be reduced. The controllable reducing of Eu3+ is explained according to the crystal structure of the host. Utilizing site selection to control the reducing of Eu3+ is considered as an alternative strategy to design novel Eu3+ and Eu2+ codoped inorganic phosphor.