In this paper, the vacuum sealing method to enhance a base vacuum level was adopted, and the resultant changes in the MgO characteristics, such as firing voltage, MgO sputtering rate, MgO hardness, and photoluminescence, were examined in comparison with those in the conventional sealing method in the 42-in. AC-PDP with a high Xe (15%) content. The 42-in. panel fabricated by the vacuum sealing method caused the changes in the MgO characteristics, such as firing voltage, MgO sputtering rate, MgO hardness, and photoluminescence, which are caused by an increase in the oxygen vacancy of the MgO layer.