Tension-Leg Platform (TLP) is a vertically moored floating structure. The platform is permanently moored
by tendons. Surge equation of motion of TLP is highly nonlinear because of large displacement and it should be solved with perturbation parameter in time domain. This paper compare the dynamic motion responses of a TLP in regular sea waves obtained by applying three method in time domain using MATLAB soft ware. In this paper Lindstedt- Poincare method (L-P method) is used to solve nonlinear differential equation of surge motion considering first-order perturbation. Also modified Euler method (MEM) is used for solving nonlinear equation of motion as numerical method and ordinary differential equation is used for linear equation of motion (without nonlinear term). The results were obtained as responses represent good accordance
between results of L-P method and MEM.