Precisely predicting the fatigue life of taut-wire mooting systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of mooting lines in a rough sea environment especially in deep waters.In this paper,a comprehensive fatigue analysis is performed for a polyester taut-wire mooring system of an FPSO based on the time domain dynamic theory,rainflow cycle counting method and linear damage accumulation rule of Palmgren-Miner.Three influential factors in the fatigue analysis including the pre-tension,dynamic stiffness and T-N curve are investigated in detail.Two polyester T-N curves,one is from the DNVOS-E301 and the other is from the API-RP-2SM,are adopted in the calculation.The fatigue analysis of the mooring system after one-line failure is also carried out.The calculation results indicate that the fatigue life is significantly affected by the T-N curve.The fatigue life decreases with increasing pre-tension,and is largely reduced if taking into account the dynamic stiffness caused by cyclic loading.The analysis also proves that one-line failure has remarkable effects on the fatigue lives of other mooring lines.The present parametric and comparative study is believed to be meaningful to further understanding of the taut-wire mooring system for deepwater applications.