The　derivative-based　traveling　wave　protection　method　has　the　problem　of　operation　failure　when　high-impedance　faults　occur.　In　this　paper,　the　characteristics　of　the　fault　initial　traveling　wave　in　DC　transmission　lines　were　analyzed　first,　and　the　expressions　of　the　fault　initial　traveling　waves　at　the　protection　installation　site　when　internal　and　external　faults　occur　were　derived　respectively.　Then　the　physical　meaning　of　each　part　of　the　fault　initial　traveling　wave　expression　was　analyzed,　and　the　exponential　coefficients　reflecting　the　fault　location　not　affected　by　the　fault　impedance　were　extracted　by　the　fitting　method.　On　this　basis,　the　principle　of　non-unit　traveling　wave　protection　for　VSC-HVDC　transmission　line　using　fault　current　initial　traveling　wave　fitting　was　proposed.　The　simulation　results　show　that　the　obtained　exponential　coefficient　can　effectively　reflect　the　location　of　fault.　The　proposed　protection　method　can　complete　fault　identification　within　1ms,　even　with　high　fault　impedance.　Furthermore,　the　influence　of　the　sampling　frequency　and　noise　on　the　protection　method　was　analyzed　and　verified.　The　results　show　that　the　proposed　protection　method　has　high　robustness　to　the　change　of　sampling　frequency　and　the　influence　of　noise.　©　2021　Chin.　Soc.　for　Elec.　Eng.