The　transient　time-domain　and　phase-frequency　characteristics　of　single-phase　grounding　fault　are　analyzed　and　a　method　of　self-adaptive　faulty　line　selection　is　proposed　for　resonant　earthing　system,　which　adjusts　the　frequency　band　interleaving,　selects　the　wavelet　function　with　better　performance　to　prevent　the　wavelet　aliasing　for　proper　faulty　line　selection,　applies　the　proportion　factor　and　transient　factor　to　reflect　the　main　components　and　transition　resistance　respectively,　and　realizes　the　adaptive　faulty　line　selection　by　the　comparison　of　amplitude　and　polarity　and　the　assistant　criterion　according　to　different　values　of　the　two　factors.　Simulative　results　show　the　proposed　method　has　higher　reliability,　suitable　for　different　types　of　single-phase　grounding　fault.