Controlling　by　rock　mass　structure,　the　stability　of　rock　mass　in　meizoseismal　areas　is　particularly　prominent.　In　this　paper,　the　dangerous　rock　mass　along　the　Ludian　National　Highway　in　Yunnan　was　taken　as　a　typical　example.　A　method　to　visually　identify　structural　planes　and　quickly　extract　characteristic　information　by　using　point　cloud　directly　was　proposed.　Firstly,　based　on　the　point　cloud,　the　random　Hough　algorithm　and　the　Fuzzy　C-means　algorithm　were　used　for　clustering　analysis.　Then　the　Fast-Marching　algorithm　was　applied　to　reconstruct　the　dominant　structural　planes　in　three　dimensions,　to　realize　the　characteristic　information　extraction　of　geometric　information　and　spatial　distribution　state　of　structural　planes.　Meanwhile,　based　on　the　extracted　characteristic　information　of　structural　planes,　combined　with　HSV　technology,　the　in-situ　dangerous　rock　mass　was　identified　and　counted.　The　Monte　Carlo　simulation　was　also　used　to　compute　the　in-situ　rock　volume　distribution.　Finally,　the　kinematic　analysis　of　the　dangerous　rock　area　was　carried　out　to　judge　the　instability　failure　mode　of　the　dangerous　rock　mass.　The　research　results　have　a　certain　reference　value　for　the　investigation　and　evaluation　of　road　dangerous　rock　mass　in　meizoseismal　areas　and　the　energy　level　design　of　protective　structures.　©　2022,　Science　Press.　All　right　reserved.