Abstract: The steel roof of China Expo Exhibition Center C1 zone belongs to a very large structure． It has a large gross floor area and high storey． In order to avoid the aerial work，the main roof trusses were preassembled on the ground and temporary steel supports were set up to lift the segments． In order to ensure the reliability of installation， six tower cranes were set up，of which four on the floor and two on the ground． Through simulation of the whole process of construction，the stress and displacement of components were forecast，which guaranteed the force and deformation of structures to be in a safe state，which provided a strong technical support for rational construction．