Abstract: The rung-shape long-span tensile cable-membrane structure in Foshan Century Lotus Stadium was conducted to investigate its dynamic responses under earthquake waves when its cable's prestressing was changed.Results show that the structure's stiffness increases with increasing the prestressing of the cable system.At the same time, the vertical displacement of the cable system decreases under seismic loading, but other members' vertical displacement and their internal force increase.And the damage by seismic action to the structure also increases.The slacking of some cables' prestressing has little effects on the axis stress of the cable system and the compression ring, but more effects on their displacement.It has also more effects on the bending moment of the compression ring and the truss web.The damage of the structure can be identified by monitoring the changes of its displacement and internal force.