Taking the Wuhan Yangtze River Flood Control Model Test Hall as the engineering background, a new hybrid spatial structure system is proposed: arch supported prestressed grid structure. Combined with the characteristics of the structural system, from the angle of initial cable deformation, the stiffness method theory of the structure is established, and the mixed influence matrix method, cyclic iterative approximation method, "sequential analysis method" of initial cable deformation, and "sequential analysis and reverse Iterative method" of cable tension are proposed for the analysis of the whole process of prestress of the structure, which is not only applicable to arch supported prestressed grid structures, It is also applicable to other similar hybrid spatial structures. Finally, the accuracy and effectiveness of this method were verified through an actual calculation example of the Yangtze River Flood Control Model Test Hall project