The raw materials of La3+ ion-doped Y0.998Pr0.002InGe2O7 phosphor were mixed by a vibration mill method, then calcined at 1200 ℃ for 10 h in air by a solid-state reaction. Regardless of the La3+ ion doping concentration, the La3+ ion did not change the crystal structure, but the luminescence properties including both the excitation and emission intensities did change. The saturation emission intensity excited by a deep UV light for the phosphor increased when the La3+ ion doping content was 10 mol%. As the La3+ ion with a large radius was introduced as a substitute for the Y3+ ion with a small radius in the Y0.998Pr0.002InGe2O7 system, an increase in compressive strain led to a decrease in oxygen vacancy concentration, which changed the emission intensity of 1D2→3H4 and 3P0→3H4 radiations for Pr3+ ion 4f–4f transition. The Commission Internationale de L’Eclairag (CIE) color coordinates of the La3+ ion-doped Y0.998Pr0.002InGe2O7 phosphor shifted slightly, but all were in the white light region at various La3+ ion doping contents. This provides an intelligent method for improving the luminescence properties of Y0.998Pr0.002InGe2O7 single-phased white light-emitting phosphors for white LEDs. In addition, various emission intensity ratios of the 1D2→3H4 and 3P0→3H4 radiations enable the phosphors to be applied to oxygen gas sensors.