Abstract: The topographic measurement of high-steep to upright slopes of complex terrain and the establishment of three-dimensional numerical models have always been puzzling geologists. In recent years, the unmanned aerial vehicle(UAV)has been widely used in geological surveys due to its small size, maneuverability, and the ability to acquire high-resolution images. This paper focuses on a new measuring and modeling method for high-steep/upright slopes with integration of UAV and many software. Firstly, on the basis of low-altitude UAV tilt photography, the Agisoft Photoscan 3D real scene modeling software and reverse engineering-based Geomagic Studio's powerful point cloud data processing function, we generate the topographic maps of high-steep/upright slope with complex terrain quickly, combine with the topographic mapping function of CASS. Subsequently, the high-steep/upright slope closed CAD surface models of complex terrain are reconstructed utilizing the CAD surface modeling function of Geomagic Studio. Then we take the advantages of the powerful geometric processing and meshing ability of Hypermesh to mesh the CAD surface models, before establishing a fine three-dimensional(3D)numerical model for high-steep/upright slopes of complex terrain. Finally, the 3D numerical model is converted into a file recognizable by FLAC^3D for calculation and analysis. In order to illustrate this method in details, we take the Feitian Waterfall Scenic Spot in Shenxianju Scenic Spot in Zhejiang Province as an example. The results indicate that the use of UAV enables fast, efficient and accurate mapping and 3D modeling of high-steep/upright slopes in complex terrain. The method has the advantages of being simple and practical, fast and convenient, and strong practicality.