A submarine is used to connect the main grid and the island grid for electricity supply. The stability performance of the cable laying vessel under complex ocean environmental conditions is important for the construction operation. In this article the effects of the cable landing operation on the stability of the submarine cable laying vessel are studied numerically. A numerical model based on ANSYS-AQWA is established for the vessel, the mooring lines, and the landing cable, which has been validated by corresponding experimental data. It is found that a mooring angle of 45° for four anchoring lines and a reasonable length extension of the cable during landing will ensure the safety of the cable and maintain the stability of the vessel.