The mooring system is the key structure of a floating platform, which plays an important role in ensuring the safe production of the platform. It is of profound significance to understand and evaluate the safety status and risk level of the mooring system in time. Aiming at the difficulties of real-time in-situ detection of mooring lines under the platform field operation states, a reliability assessment method of catenary mooring system based on prototype monitoring information is proposed in this paper. Compared with the conventional Monte Carlo simulation, the proposed reliability assessment model can improve the calculation efficiency to meet the requirements of real-time reliability analysis. Firstly, based on the catenary equation, a numerical simulation analysis of the forcing behavior of the mooring line was performed considering the influence of the current load. Then, a reliability assessment modelling method for strength analysis and fatigue analysis of mooring system was proposed based on Enhanced Monte Carlo (EMC) method. Finally, based on the prototype monitoring data of a semi-submersible platform in the South China Sea, the reliability assessment of the mooring line was performed by taking into consideration the impact of the corrosion. The simulated results indicate that the present real-time reliability assessment method could provide a superior ability for the guidance of the safety assessment and maintenance of catenary mooring system.