Li + , Na + , or K + co-doped CaO: Eu3+ phosphors were prepared by the combustion synthesis method and characterized by X-ray diffraction (XRD), photoluminescence and photolumi- nescence excitation (PL-PLE) spectra. The experimental results show that, upon excitation with 250 nm xenon light, the emission spectrum of the CaO: Eu3+ consists of 4f-4f emission transitions from the 5D0 excited level to the 7FJ (J=1, 2, 3) levels with the mainly electric dipole transition 5D0→7F2 of Eu3+, indicating that the Eu3+ occupies a low symmetry. The charge-transfer band (CTB) shows somewhat red shift with the decreasing ionic radii of co-doped alkali metal ions. The PL and PLE intensities are significantly enhanced, especially the strongest intensity of luminescent is CaO: Eu3+, Li + phosphor, when alkali metal ions are incorporated. The strongest peak of emission is slightly shifted from 614 to 593 nm, indicating that the Eu3+ ion locates in a symmetric position (Oh) when alkali metal ions are incorporated. Li +, Na +, or K + co-doped CaO: Eu3 + phosphors were prepared by the combustion synthesis method and characterized by X-ray diffraction (XRD), photoluminescence and photoluminescence (PL-PLE) spectra. show that, upon excitation with 250 nm xenon light, the emission spectrum of the CaO: Eu3 + consists of 4f-4f emission transitions from the 5D0 excited level to the 7FJ (J = 1, 2, 3) levels with the mainly electric dipole transition 5D0 → 7F2 of Eu3 +, indicating that the Eu3 + occupies a low symmetry. The charge-transfer band (CTB) shows somewhat red shift with the decreasing ionic radii of co-doped alkali metal ions. The PL and PLE intensities are significantly enhanced, especially The strongest intensity of luminescent is CaO: Eu3 +, Li + phosphor, when alkali metal ions are incorporated. The strongest peak of emission is slightly shifted from 614 to 593 nm, indicating that the Eu3 + ion locates in a symmetric position (Oh) when alkali metal ions are in corporated.