In　order　to　improve　the　fault　monitoring　performance　of　grounding　electrode　lines　in　ultra-high　voltage　DC　(UHVDC)　transmission　systems,　a　novel　fault　monitoring　approach　based　on　the　high-frequency　voltage　standing-wave　ratio　(VSWR)　is　proposed　in　this　paper.　The　VSWR　is　defined　considering　a　lossless　transmission　line,　and　the　characteristics　of　the　VSWR　under　different　conditions　are　analyzed.　It　is　shown　that　the　VSWR　equals　1　when　the　terminal　resistance　completely　matches　the　characteristic　impedance　of　the　line,　and　when　a　short　circuit　fault　occurs　on　the　grounding　electrode　line,　the　VSWR　will　be　greater　than　1.　The　VSWR　will　approach　positive　infinity　under　metallic　earth　fault　conditions,　whereas　the　VSWR　in　non-metallic　earth　faults　will　be　smaller.　Based　on　these　analytical　results,　a　fault　supervision　criterion　is　formulated.　The　effectiveness　of　the　proposed　VSWR-based　fault　supervision　technique　is　verified　with　a　typical　UHVDC　project　established　in　Power　Systems　Computer　Aided　Design/Electromagnetic　Transients　including　DC(PSCAD/EMTDC).　Simulation　results　indicate　that　the　proposed　strategy　can　reliably　identify　the　grounding　electrode　line　fault　and　has　strong　anti-fault　resistance　capability.