Pr 3+ -doped Gd 2 O 3 phosphor powders were prepared by co-precipitation method. Their structures during heat-treatments were studied by XRD and IR methods. The pH was optimized to be 8 in the co-precipitation process and the hydroxide precursors were transformed into pure phase cubic Gd 2 O 3 at 500°C for 1h. Optical properties of Pr:Gd 2 O 3 phosphor powders were reported. The main emission bands are assigned to 1 D 2 → 3 H 4 , 3 P 0 → 3 H 6 , 3 P 0 → 3 F 2 transition of Pr 3+ under excitation at 255 and 488nm. The emission intensities increase with increasing sintering temperature. Concentration quenching appears as the Pr 3+ doping-concentration up to 1at.%.