Abstract: In order to improve the safety of the information acquisition process of the slope structural plane and the accuracy of the measurement results， the multi-angle photogrammetry of the unmanned aerial vehicle(UAV) is used to obtain the structural plane information， and the coordinates of the slope structural plane and the length of the exposure are obtained. A dynamic Delaunay triangulation is proposed to triangulate the model. The stability analysis of the exposed surface of the slope is carried out in combination with the block generation rule. The key block is identified on the slope and the GeoSMA-3D is used to verify the feasibility and accuracy. The results show that the maximum key block of point cloud cutting is 38.5748m³， and the maximum key block of GeoSMA-3D cutting is 38.5617m³. Meanwhile， the blocks are both in the center of the slope. For irregular fractured rock slopes， 3D point cloud cutting can better characterize the block position of 3D slopes， and it has certain advantages for guiding key block management.

Key words: UAV(unmanned aerial vehicle), structural plane, block, rock slope, Delaunay triangulation