Long-span hybrid structures have been widely used in recent years. Composition and working mechanism of cable-strut-supported rigid shell structure of a gymnasium roof are analyzed in this paper. Influences of different type of supports and bracing members on the spatial working property of this hybrid structure and factors that influence stiffness of the structure are analyzed too. Analysis results identify the formation mechanism of spatial stiffness of the hybrid structure. The research results can shed light on study and designing of the same kind of structure.