Abstract: As a key connecting part of the gravity-type liftable cage grid-type mooring system, the length of the connecting rope not only decides the diving depth of the cage but also plays a crucial role in ensuring its safety and stability. In this study, we compared the physical model of a gravity-type liftable cage grid-type mooring system with different connecting rope lengths at different wave directions in terms of cage motion response and mooring force. The results show that the maximum reduction of the surge of the cage was 37.28% and the maximum decrease in heave was 28.97% with short connecting ropes, which proves that the short connecting ropes can effectively limit the surge and heave movement of the cage, and enhance the stability of the cage. However, compared with the long connecting ropes, the mooring force of the mooring system with short connecting ropes was larger. Thus, it is suggested that the stability and safety of the cage should be taken as the primary consideration, the short connecting ropes should be selected to enhance the stability of the cage under the premise of meeting the design diving depth of the cage, and the mooring design should be strengthened to ensure the safety of the mooring system.