Remotely operated vehicles (ROVs) are frequently used in subsea explorations and exploitations, aiming to obtain not only traditional ocean oil and gas, but also other mineral resources, such as manganese, polymetallic nodules and sulfides. However, due to the interactions between ocean environmental loads, ROV, suspending cable and top-end vessel, the dynamic responses of ROV system have strong coupling and nonlinear characteristics. Especially, during the initial deployment and the final recovery stages, the cable length might be so short that the relative motion between the ROV and the vessel may cause a severe collision and even structural damage. In this study, based on the structural and dynamic characteristics of the ROV system during the initial deployment and the final recovery stages, numerical simulation and analytical method are employed to investigate the impacts of the top-end vessel motion on the ROV system. In the numerical simulations, vessel surge and hydrodynamic force on ROV, are considered, and the ROV responses and cable tensions under different vessel motion amplitudes and frequencies are presented. It is found that the ROV responses are larger than the vessel motion amplitudes in some cases owing to vessel surge. And, the governing equation of ROV with a horizontal moving boundary is developed. Then, in order to have a deeper understand of the behaviors of the ROV system and the mechanisms of our simulation results, the analytical method is used.