Abstract: Support structure system of air cooled condenser is an important component in a thermal power plant,the security of the structure directly related to the normal operation of the power plant. Spatial steel truss-reinforced concrete pipe column vertical hybrid structure, whose stiffness and mass is badly non-uniform at vertical direction, is used in the traditional 300 MW and 600 MW unit thermal power plants. Compared with the 300 MW and 600MW unit power plants,processing set-up and support structure have changed in 1 000 MW unit power plant,the risk that caused by deterioration of the structure is fearful. Because of the torsional effect and the coupling effect between the modes are obvious in this kind of structure,multidimensional earthquake response analysis,in which torsional components of ground motion is considered,is put forward in this paper to study the force transmission mechanism. Research results show that lateral-torsional coupled seismic design should be considered severely in this kind of vertical hybrid structure.