An alternate application of MgO film for the improvement of discharge characteristics and lifetime in an ac plasma display panel (PDP) is suggested. In the normal ramp reset, the accumulated wall charges on the phosphor surface just after the reset period are different as to their color (red, green, blue) of each phosphor, which reduces the common voltage margin of ac PDP. In general, MgO is used for the protective layer of dielectrics from ion sputtering and the improvement of secondary electron emission which affects the driving voltage in an ac PDP. In this research, we deposited MgO on the phosphor to get the same addressing characteristics irrespective to the color of each phosphor, high speed addressing, and prolonged lifetime of phosphor despite the vacuum ultraviolet irradiation and ion bombardment. An optimized MgO thickness was used to avoid the excessive luminance and luminous efficacy degradation by the MgO deposition on the phosphor. Results showed that PDP with MgO coated phosphor has more uniform formative delays in address discharges and improved degradation characteristics.