Under the conditions of the marine environment (wind, wave, current), the floating platform on the ocean undergoes heeling, trimming, rolling, pitching, swaying, surging, heaving movements. The floating reactor on the floating platform within the design life, in addition to withstand the low-frequency fatigue caused by primary loop temperature and pressure, it also has to withstand the inertial force generated by the sway of the wave for the service period. The inertial force generated by the wave is a constantly changing dynamic load. Alternating stresses inside of the structure may cause fatigue damage to the structure. In order to estimate the fatigue life of floating reactor equipment under various ocean conditions, a finite element analysis model of equipment was established to carry out research for fatigue analysis methods under sway loads, meanwhile the operating temperature and pressure loads were considered. The probability of sway at each angle obeys the Rayleigh distribution, through the analysis of the status for the platform, it can estimate the number of swings at each angle. Based on Miner linear cumulative damage theory, the cumulative fatigue usage factors meet the requirements of the ASME BPVC III NB-3220 code. This analysis method provides a reference for the fatigue analysis of the floating reactor nuclear equipment.