When　single　phase　to　grounding　fault　occurs　on　a　small　current　neutral　grounding　system,　the　transient　high　frequency　signal　on　the　zero　sequence　current　includes　messages　that　can　distinguish　fault　line　and　non-fault　lines.　Using　Morlet　wavelet　transform　on　this　signal,　by　the　modulus　and　phase　of　the　wavelet　transform　results　the　fault　line　can　be　accurately　picked　out.　The　paper　presents　this　method.　The　simulation　and　experiments　in　lab　verified　the　effectiveness　and　reliability　of　this　method.