In order to improve the material properties of the protective layer for alternating current plasma display panels, small amount such as BeO elements was added to the MgO protective layer. The electrical properties of Mg1-xBexO film deposited by an electron beam evaporation were investigated. The experimental results reveal that the discharge voltage of PDP device with the Mg1-xBexO film, when the concentration of BeO was 40 at.%, was reduced by 20 V, compared with the conventional MgO film. To elucidate the reason for increasing the secondary electron emission, the change in the energy band structure was investigated by measuring PL. The experimental results show the defect level of the Mg1-xBexO films increases to a large extent in comparison with that of the conventional MgO film. It also implies that the secondary electron emission has a strong correlation with the energy band structure, related to the defect levels originating from doping and thence resulting in changes in the associated electrical characteristics.