The architectural technology and art of the timber-frame buildings are precious wealth in the Chinese cultural heritage; however there are a few relics in China and even a few literal records about that. Using the VR-orientated 3D modeling technology to reconstruct the ancient buildings is a critical approach for researching and protecting the historic relics. The LOD-CAD modeling measures those 4 discrete LOD models are established for every building is discussed particularly, and models are decomposed into several appropriate parts according to the structural feature of the buildings and limitation of data quantity. The discrete models are organized in LOD-R-tree spatial index, and a strategy of minimizing the change of rendering state is addressed for obtaining interactive frame rate. For improving the image quality of rendering GPU-based shaders are developed, and occlusion culling, DDS texture format, and Vertex Buffer Object are employed to raise rendering efficiency.