The traditional two dimension plans and elevations of ancient structure have limited the applications of maintenance and reconstruction and can not satisfyd the current requirements. Based on the architectural survey project of the "Chi Lin Nunnery Redevelopment" in Hong Kong, which has been carried out during 1996~1998, this paper attempts to investigate the methods and techniques of computer-based 3D simulation and database building of the whole engineering for large-scale timber structure, which enables the quality control. There were several key issues including primary data acquisition, 3D modeling and display, assembling the total structure before reconstruction and the quality examination, etc. In this paper, some useful experiments such as the new applications of CCD digital cameras, image and graph processing software (CAD,Photoshop, Photomodeler) to the architectures were also presented. The methods introduced in this paper are suitable for image and graph integrated database building of complicated architectures, it is also useful for the convenient maintaining and reconstructing.