In order to investigate the hydrodynamic performance of the umbilical cable of the ROV, this paper built a mothership-umbilical cable-ROV hydrodynamic model based on the hydrodynamic software Orcaflex to simulate the operation of the ROV under offshore sea conditions and explore the hydrodynamic characteristics of the umbilical cable under different motion modes. The RAO of the mother ship was obtained by the hydrodynamic software AQWA. Based on the RAO data, Orcaflex software was used to conduct hydrodynamic simulation, and a series of hydrodynamic responses, such as the effective tension, Strouhal frequency and cable displacement, were obtained. The results show that, when the ROV is in translational or rotational motion, the restraining force at both ends of the umbilical cable is periodic; In the cable length direction, the fluctuation of the tension curve corresponding to each flow direction is gentle, and the tension in the middle is small, while the tension at both ends is large; When the cable is used as the reference point, the relative velocity and Strouhal frequency of the fluid near the ROV and the mother ship are larger. The hydrodynamic results can provide effective guidance for the hydrodynamic analysis of the umbilical cable of a small ROV.