Discharge characteristics of multi-phase AC arc were investigated for the innovative in-flight glass melting technology. The discharge behavior were studied by using high-speed video observation and the analysis of the obtained images for 2, 6, 12-phase AC arcs. The luminance area of the arc and its fluctuation were estimated to investigate the periodical characteristics of the multi-phase AC arc. Obtained results indicated that an increase of the number of the phase leads to large luminance area and faster fluctuation. Consequently, the 12-phase multi-phase AC arc is suitable for the powder heat treatment.