A multi-body coupled dynamic model is developed to simulate the motion of a Tethered Remotely Operated Vehicle (TROV) system. A strong nonlinear coupling motion between umbilical tether and ROV is discussed .The movement of ROV is considered as six-degrees of freedom. The lumped mass model is applied and an averaged tangential vector technique is included in the three-dimensional dynamic response equations of the cable-segments. The model can simulate the three-dimensional transient coupled motion of the complex multi-body system in typical ship maneuvering conditions and can be used in either a towing problem or a tethered underwater vehicle problem. Simulation results are seen to fit well with the experiment.