In this paper, the electron emission characteristics of MgO, being used as a protection and electron emission layer for ac-PDPs, were examined in relation to glow discharge, crystal structure and defects, and the physics of Auger neutralization reaction. Emphasis has been placed on basic physics associated with secondary electron emission mechanisms from MgO subjected to glow discharge environments. Based on these analyses, we extracted major parameters that may affect the yield of the secondary electron emission and discussed possibilities for improving the yield of the emission.