The nonlinear coupled in-plane vibration equations of two spans transmission line system were derived

in which the geometric nonlinearity of transmission line was considered

and the insulator string of straight tower was simplified to a rotation rigid body.The characteristic of nonlinear coupling vibration and the mechanism of energy transfer were studied under different working conditions.When the natural frequencies of two spans transmission lines have a certain relationship

the system resonance is triggered.The influences of damping coefficient of damper and its location on attenuated vibration of transmission line were analyzed

and the dampers installed on transmission line can obtain stronger vibration control effect than on insulator string.The studied results provide a theoretical base for further investigating the design of transmission line system for vibration reduction.