Abstract: When tension leg platform (TLP) moves with finite displacements, loads acting on it are response coupling. In addition, equations of motions should be set up on the instantaneous position. Such situation is different from that of the first order infinitesimal displacement. A theoretical model for analyzing the nonlinear dynamic behavior of a tension leg platform with finite displacement is developed, in which multifold nonlinearities induced by finite displacement are taken into account, e.g. coupling of the six degrees of freedom, instantaneous position, and instantaneous wet surface. Nonlinearities induced by free surface effects and viscous drag force are also included in this model. The governing differential equations of tension leg platform considering comprehensive nonlinearities are deduced. The numerical analysis of a typical tension leg platform named ‘ISSC TLP’ is performed. The nonlinear dynamic responses of the platform in regular waves with six degrees of freedom are acquired. The degenerative linear solution of the proposed nonlinear model agrees very well with published one. Furthermore, numerical results are presented which illustrate that nonlinearities exert a significant influence on the dynamic responses of the tension leg platform.