Abstract: To analyze the vibration stability of submerged floating tunnel under the uniform current, the vibration equation of tether is set up and simplified by Galerkin method, and the vibration stability of tether under the vortex-induced vibration is judged by Lyapunov exponent method. The influence of tether damping ratio, initial tension, uniform flow velocity and frequency of vortex-induced vibration on the vibration stability of tether is studied. It is concluded that the tether is gradually changed from stable state to unstable state as the current velocity increases; the tether tends to be stable as the damping ratio and initial tension of tether increase; when vortex-induced frequency is close to the 1st nature frequency of tether, the vortex-induced resonance would occur and the tether is easy to be unstable.