- Copyright 2017 by the International Society of Offshore and Polar Engineers (ISOPE). In the present study, the Finite-Analytic Navier-Stokes (FANS) code is coupled with an in-house finite-element code for time-domain simulation of the hydrodynamic response of Catenary Anchor Leg Mooring (CALM) buoy system. In the FANS code, the fluid domain is decomposed into multi-block overset grids and the Large Eddy Simulation (LES) is used to provide accurate prediction of vortex-induced motion of the buoy. The mooring system is simulated with a nonlinear finite element code, MOORING3D. An interface module is established to facilitate interactive coupling between the buoy and mooring lines. The coupled code was calibrated first for free-decay case and compared with model test data. The coupled code was then employed for the simulation of two degree-of-freedom vortex-induced motion of a CALM buoy in uniform currents to illustrate the capability of the present CFD approach for coupling mooring analysis of offshore structures. With the study it can be verified that the coupled method is able to provide an accurate simulation of the hydrodynamic behavior of the CALM buoy system.