Unloading is a complicated process that the load-carrying condition of main structure is gradually transferred and the internal force is redistributed, and so the exact numerical simulation applied on the unloading process is crucially important. The steel roof composed of the space tubular truss with the long-span and cantilevered structure for the Helan Shan stadium at Yinchuan city in Ningxia Hui autonomous region is taken as an analytical example and the finite element analysis software SAP2000 is used to simulate the unloading process during the steel construction. The computational model is established and the simulation method is provided for investigating the detailed unloading process of steel roof. The load-carrying characteristic of every bracing point acquired by the numerical simulation analysis is applied to analyze and evaluate the structural performance under two different comparable unloading cases and then an optimized unloading scheme is achieved from these two cases. The deformation of steel roof and stress ratio of steel member at each different unloading step during the whole unloading process are presented. Ultimately, based on the preferable unloading scheme, the temporary bracing structure is designed by using the maximum reaction of bracing points when unloading.