The effects of plasma treatment on the luminescence properties of BaMgAl10O17:Eu2+ (BAM:Eu2+) are investigated. Among argon-based plasmas with hydrogen or oxygen, it is confirmed that the addition of hydrogen to an argon plasma markedly improves the lifetime of BAM:Eu2+. The obtained results reveal that the oxidized Eu ions are reduced by a hydrogen plasma. Furthermore, it is found that the stability of the BAM host is also improved. As a result, BAM:Eu2+ phosphor has a higher resistance against (Ne+Xe) plasma irradiation. This new method of plasma processing for blue phosphor is applicable to the fabrication of plasma displays.