Existing　quick　or　early　detection　and　identification　methods　for　short　fault　are　based　on　the　sharp　increase　of　the　short　current　to　extract　the　fault　features　in　low-voltage　system.　They　all　have　a　technical　bottleneck　problem　of　miscarriage　of　justice,　which　is　affected　by　the　noise　of　the　distribution　system　and　the　non-fault　running　state　interference　caused　by　different　load　starting　or　switching.　On　the　basis　of　establishing　the　simulation　model　of　the　single-phase　short　in　the　low-voltage　system,　this　paper　analyzes　waveforms　of　the　faulty　branches　terminal　voltage　in　full　angle　range　and　concludes　the　characteristic　which　faulty　branches　terminal　voltage　almost　drops　to　zero　at　the　moment　of　short　circuit　and　remains　near　zero　zone　before　fault　elimination.　And　based　on　the　above　analysis,　this　paper　introduces　the　wavelet　packet　decomposition　method　and　combines　wavelet　packet　decomposition　method　with　instantaneous　value　of　terminal　voltage　so　as　to　eliminate　the　interference　of　noise　and　different　types　of　load　startup　etc.　Simulation　and　experimental　not　only　verify　the　effectiveness　and　fast　of　the　terminal　voltage　early　detection　method　for　short　circuit　but　also　solve　the　problem　of　the　reliability　of　the　existing　methods　for　early　detection　of　short　circuit　current.