Safe evacuation is the most fundamental requirement of fire safety measures in buildings. Many computer based evacuation models have been developed to quantify and model human movement in the buildings. Two methods are usually used to represent the building enclosure in these models: fine and coarse networks. This paper presents a fine network model and a coarse network model based on these methods respectively, and develops an integrated network model that integrates both network methods for efficient and detailed assessment of evacuation in large and complex buildings. To demonstrate the advantages of using the integrated network model, the results of its simulation for a highrise office building and a large shopping mall are discussed and compared to the simulation results of the fine network model and the coarse network model. It shows that the integrated model can be used to simulate evacuation in large and complex building and is adequate in representing details of the evacuation process. 