Floating structure is the basis of marine resource exploitation and marine space utilization. The performance of the mooring system directly affects the overall cost of the floating structure and its survivability in extreme conditions. For a conventional taut mooring system, significant fluctuations in tension occur in mooring lines due to the cyclic loading of waves, which will amplify the fatigue effect and reduce the cable’s service life. To overcome these issues, the authors have proposed a constant tension pulley mooring system for floating structures. The proposed mooring system consists of clump weight, pulley, and wires. Based on the time-domain potential flow theory, the motion of the floating structure and the tension in the cables were identified through the software ANSYS-AQWA. By comparing with traditional taut mooring systems, the maximum tension and fluctuation of cable tension were significantly reduced for the proposed mooring system, thereby reducing mooring system costs effectively. This study provides a promising pathway toward sustainable and reliable mooring systems.