It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface. On the basis of the architectural survey project of “Chilin Nunnery Reconstruction”, this paper investigates an easy and feasible way, that is, on project site, applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface. The method has been proved very effective in practice.