Under the background of tethered deorbit system and considering the mass and flexible factor of the tether,a deployment dynamic model for flexible tethered-assisted deorbit system was given based on the micro-element method.For the complicated nonlinear and strongly coupled dynamic equations,the dynamic model was discredited to obtain numerical solution by Galerkin method.Then a mathematic simulation was conducted to validate and analyze the dynamic characteristics of the system.The results showed that the Longitudinal and Transverse vibrations and the frequency increased with the deployment of the system,but the amplitude decreased,and the amplitude of the vibrations of the in-plane angle and tension also decreased.So the vibrations induced by the flexibility of the tether damped and tended to a quasi-stationary configuration with the increase of the deployed tether.