Abstract: For an offshore wind turbine supported by bucket foundation,based on the measured vibration data on site,the stochastic subspace identification method was used to identify the damping of the measured offshore wind turbine structure,and the damping characteristics of the offshore wind turbine supported by bucket foundation under parked and operational conditions were studied. The results show that:in parked conditions,the along-wind and cross-wind damping of the offshore wind turbine supported by bucket foundation both increase with the increase of external wind speed,and the average values of these are 0.952% and 0.973%,respectively;in operational conditions,the along-wind damping shows an increasing trend with the increase of external wind speed,and its average damping value varies within the range of 3.87%-5.28%. For the cross-wind damping,its change trend is less affected by the external factors. The average value of cross-wind damping varies from 1.74% to 3.37% in the entire wind speed range,and the crosswind damping is smaller than the along-wind damping under operational conditions.