Abstract: In major and complex projects such as large-scale hydropower and high-speed railways in our country, large-scale irregular mesh surfaces and complex solid shapes are widely involved, and there is often a need for the coexistence and interaction of mesh models and solid models. To solve this difficult problem, this paper proposes an efficient fusion technology of mesh model and solid model. This method achieves the organic combination of the efficient computational advantages of mesh model and the high-precision geometric expression capabilities of solid model through three core steps: data preprocessing, data transformation, and data fusion of multi-source heterogeneous models. The research first conducts data cleaning, topology repair and geometric optimization on the mesh model, and performs closure, connectivity repair and redundancy cleaning on the solid model. Secondly, convert the two into a mesh-solid hybrid model with a consistent structure; Finally, through the improved bounding box detection, precise model intersection, intersection edge ring formation, ring combined surface, and surface encirclement combination algorithms, the deep Boolean fusion and integrated rendering of the model are achieved. It was also applied on the Yangfanggou hydropower station on the Yalong River in the Yangtze River Basin. The results show that this technology can effectively support the integrated modeling and rendering of "geological-structure" in water conservancy and hydropower projects. This research provides a universal technical path for the digital modeling of complex projects in multiple fields such as water conservancy and hydropower, transportation hubs, and large-scale buildings. It breaks through the application limitations of traditional single models and has extensive engineering application value and promotion prospects.