For　the　first　time,　this　paper　reveals　and　explains　the　details　how　to　comprehend　and　deduce　the　evolution　of　current　filaments　in　FRD　by　the　negative　resistance　phenomenon　presented　in　reverse　recovery　I-V　curve.　Further　study　on　simulation　data　shows　that　the　curve　shape　of　voltage　clamping　period　is　caused　by　the　generation　of　solitary　filaments,　and　the　definite　correspondence　relationship　of　them　is　discussed.　©　2019　IEEE.