Landslides are a common geological hazard, often induced by extreme weather events such as heavy rainfall. In this study, a UAV-mounted LiDAR (laser radar) system is used to acquire post-disaster high-precision point cloud data, generate post-disaster digital elevation models (DEMs) through point cloud data processing, and compare and analyze them with pre-disaster publicly available DEM data, to achieve accurate quantification of the extent and volume of landslides triggered by typhoons. The study took the landslide of a quarry in Tokyo, Japan as an example, and acquired high-density point cloud data of 210 million points within an area of about 0.3 km2. The results show that the total area of the landslide amounts to 132,945 m2 with a maximum depth of 35.9 m and a total volume of about 52,290 m3. The study confirms that the method can quickly obtain information on post-disaster topographic changes and provide a scientific basis for disaster assessment and prevention.