This paper deals with the issues involved during the design of a complex roof structure in the grand theater located at the city of Hangzhou, China. The complexity comes from the structural being of three reasons: long-span, complex structure and special figuration. To study the roof structure completely, researches on the mechanical properties of the structure are carried out in the paper. The nonlinear finite element method is used to analyze the geometrical nonlinear stability. Buckling and post-buckling analyses are performed to determine the load-carrying capacity of the perfect and imperfect roof structure. Meanwhile, the critical loads of the structure with different parameters are also discussed in this paper. It is shown that the effect of supporting stiffness originated from foundations and concrete structures to improve the critical load is evident. The buckling of the structure is a global collapse. With the temperature rises, the limited load-carrying capacity of the structure decreases obviously.