Abstract: To address the collaborative challenges of geometric accuracy, rendering efficiency, and scene adaptability in large-scale CAD model visualization, this paper proposes an architecture deeply integrating Qt, Open CASCADE (OCC), and Open Scene Graph (OSG). The architecture adopts a layered and decoupled design: Qt manages UI interaction and graphics environment, OCC handles Boundary Representation (B-Rep) modeling and precise meshing, while OSG focuses on real-time rendering and camera control, with low-coupling communication achieved through OsgQOpenGLWidget and OsgRenderer. In this paper, the two-engine collaboration mechanism is studied. The triangular mesh generated by OCC is converted into OSG format by custom functions. Combined with orthogonal projection and millimeter-level camera control to ensure size correspondence, the performance is optimized by strategies such as geometry merging. Additionally, the system constructs a multi-dimensional extension framework, supporting flexible customization of interaction tools, modeling algorithms, and rendering effects. Case tests show that the architecture maintains a high frame rate in scenarios with a large number of components. It balances engineering-level accuracy and real-time interaction requirements, applicable to diverse CAD scenarios such as architecture and machinery, effectively resolving the core contradictions in large-scale model visualization.