Series arc fault experiment platform was built with reference to the domestic existing research results and the United States UL1699 standards. The data of arc current and arc voltage were collected. According to the characteristic harmonics that was obtained by FastICA analysis, the separated independent component and wire’s current were analyzed by harmonic ratio respectively. When arc fault occurred, the typical variation characteristics of harmonic ratio was summed up. Research results show that: when arc fault occurred, the harmonic ratio of independent component change very obviously, but the harmonic ratio of wire’s current does not grow up by much. Even in load’s some running conditions, some harmonic ratio growth is zero.