The rapid development of offshore electricity grid construction has led to a great demand for submarine cable deployment. In this study, a numerical model is established based on the commercial software ANSYS-AQWA to investigate the dynamic interactions between a cable-laying vessel and a submarine cable during its landing process, which has not yet been reported and is critical to the safety of the cable. The numerical model was validated by an experimental test on the mooring stability of a vessel conducted in a wave tank. The effects of the cable length, the current velocity, the incident wave, and the wind direction on vessel stability and the tensions in the mooring lines and cable were investigated. When the cable length is short, the submarine cable acts as a mooring cable that can stabilize the hull, but it is not safe to apply force to the submarine cable. At the same time, an increase in the current speed also increases the tensile force of the submarine cable. The influence of different incident wave directions and wind directions on the stability and tension of ships in mooring lines and cables was studied, and the most unfavorable environmental conditions for submarine cable laying were determined under different environmental conditions.