The fatigue calculation and analysis method is studied for the mooring system of large floating wind turbine. The dynamic tension of the floating wind turbine mooring system is time-varyingand asymmetric about the time axis. The effect of the average cyclic stress is ignored in the current fatigue analysis of floating wind turbine mooring lines. Only the effect of the asymmetric peak of the mooring tension is considered to calculate the fatigue damage. The Goodman equation is introduced to correct the asymmetric peak value of mooring line stress by considering the average cyclic stress value of the dynamic tension. The critical fatigue cycle number is determined based on the corrected peak value of different stresses to calculate the fatigue damage. Based on the Goodman equation correction method

the fatigue damage and fatigue life of 10 MW wind turbine were calculated. The results show that the cycle-averaged stress value of the mooring line has an important influence on the fatigue damage

and the Goodman equation should be introduced to correct the asymmetric stress peaks in the fatigue analysis

the fatigue performance of the 10 MW wind turbine mooring system meets the safety requirements.