For　high-voltage　direct　current　(HVDC)　transmission　systems,　the　transient　fault　current　characteristics　are　that:　if　the　fault　point　is　over　the　line,　the　fault　component　current　measured　at　both　converter　stations　would　be　increased　and　they　have　the　same　changing　direction.　If　the　fault　point　is　beyond　the　line,　the　fault　component　current　measured　at　one　converter　station　is　increasing　and　the　fault　component　current　measured　at　the　other　converter　station　is　decreasing,　so　they　have　the　opposite　changing　direction.　According　to　this　characteristic,　a　novel　pilot　protection　principle　for　HVDC　transmission　line　based　on　fault　component　current　is　proposed　here.　The　principle　proposed　has　no　limitation　to　the　sampling　frequency.　A　fault,　whether　it　occurs　in　the　line　or　beyond　the　line,　can　be　effectively　identified　only　using　the　fault　component　current　at　both　converter　stations.　At　the　same　time,　the　setting　criterion　of　the　fault　component　current　is　also　given.　The　simulation　results　show　that　the　new　method　can　identify　the　faults　reliably　and　rapidly.　The　study　is　promising　to　have　significant　theoretical　and　practical　value.