Abstract: The traditional three-dimensional modeling technology of existing buildings has problems such as low model integrity and lack of architectural information in the construction of digital campus scenes. This paper proposes a technical system of 'multi-source mapping-data fusion-reverse modeling'. Through the cooperation of UAV tilt photography and 3D laser scanning technology, millimeter-scale geometric shape data and high-resolution texture information of buildings are obtained. The improved SICP algorithm is used to realize the accurate fusion of multi-source point clouds. Finally, BIM technology is used to reversely construct a refined digital model containing a large amount of building information. The research results show that the reversely constructed BIM model achieves high completeness and centimeter-level geometric accuracy, which realizes the integration of multi-dimensional building information. This study can provide a full life cycle digital basis for digital campus scene construction, human-computer interaction and operation and maintenance management.