Underground　engineering　is　full　of　difficulties　and　risks　during　tunnel　construction,　and　observational　monitoring　is　becoming　more　and　more　important　in　the　course　of　tunneling　construction.　Using　3D　laser　scanning　measurement　technology,　and　based　on　3D　point　cloud　monitoring,　a　comparative　analysis　is　carried　out　in　terms　of　the　tunnel　excavation　process,　deformation,　and　clearance　intrusions,　the　purposes　of　which　are:　(1)　to　trace　tunnel　settlement,　convergence,　stress　and　deformation;　(2)　to　provide　a　dependable　basis　for　adjusting　the　support　parameters,　installing　the　secondary　lining　at　an　optimum　time,　and　modifying　the　design　scheme;　and　(3)　to　provide　early　warning　and　alarms　and　risk　management　based　on　monitoring　results.　Engineering　practices　indicate　that　the　3D　laser　scanning　system　is　characterized　by　high　speed　and　high　precision,　and　its　measurement　precision　meets　the　specified　requirements　with　the　data　being　very　close　to　that　of　the　Leica　TPS1200　total　station.