Abstract: The steel roof of a gymnasium is a hybrid tension structure with pre-stressed truss shell system. The finite element method was used to analyze the mechanical behavior of the roof structure under temperature rising and cooling. The results show that high temperature results in the yielding of structural components and the development of plastic deformation; significant residual stress and deformation are observed after the temperature drops to room temperature. Temperature rising and cooling incurs large support reactions, which is harmful to the structure, especially when the temperature rising and cooling occurs in the central area of the roof structure. Hence, flameproof should be paid more attention for the central area of the structure.