Abstract: The reasonable transverse isolation system of typical long-span single-tower cable-stayed bridges with hybrid girders for mountainous areas was investigated.Based on the Jinsha River Bridge,the structural significant asymmetry,dynamic characteristics and seismic responses were analyzed.A method using influence matrix for calculating the reasonable damper parameters of the isolation system was proposed,and its convergence and the influencing factors were discussed by taking triangular steel dampers as an example.The results show an obvious correlation between the reasonable damper yield forces of the transverse isolation system and the corresponding bearing shear forces of the transverse fixed system,and proper initial yield forces and influence matrix could significantly improve the efficiency and stability of the iteration process.The effects of the local terrain on the reasonable yield forces of the dampers at different positions of the cable-stayed bridge were further analyzed based on the relative lateral stiffness ratio of the auxiliary piers to the transitional pier.In the case of the side span over a steep slope,it is recommended dampers be installed at all tower and pier locations,so that the relative displacements between the auxiliary piers and the girder and the seismic responses of the tower and piers could be well controlled; whereas in the case of a gentle slope,dampers could be set only at the tower and transitional pier locations,where a similar damping effect as the case of the dampers set at all tower and pier locations could be achieved.