To investigate the maneuvering response of large offshore Gravity-Based Structures (GBSs) during towing operations, this study develops an unsteady CFD simulation model for towing maneuverability based on the STAR-CCM + platform. The model integrates the body force propeller method, catenary cable theory, and multi-body dynamic coupling techniques. Standard Zig-Zag maneuver tests are designed to conduct a comparative analysis between a single towing vessel and a coupled towing-GBS system. The results indicate that the presence of the GBS significantly alters the heading response of the system, suppressing the turning tendency of the towing vessel and notably reducing the first overshoot angle, thereby resulting in a more stable maneuvering process. The time histories of cable tension exhibit a bimodal pattern correlated with the oscillation period of the heading angle, primarily caused by velocity mismatches between the towing vessel’s turning motion and the delayed response of the towed object. This reflects the dynamic damping effect of the cable connection system on transverse disturbances. The towed GBS displays a characteristic three-degree-of-freedom response during the maneuver, including gradually amplifying roll, small-amplitude pitch, and coupled yaw-heading motions. The findings provide valuable insights for evaluating the maneuverability and layout parameter design of large floating towing systems.