Abstract: The offshore wind power structures bear complex environmental loads induced by winds and waves over the life time. Dynamic characteristic is an important basis for the safety assessment of the offshore wind power structures. Based on the in-situ test data of offshore wind power on composite bucket foundation in Rudong county of Jiangsu Province, the structural modal parameters under different environmental excitations are identified, and the evolution laws of dynamic characteristics of offshore wind power with environmental excitations and time are analyzed. The results show that the modal frequency and damping ratio of the offshore wind power obey the normal distribution, and exhibit a certain degree of dispersion. The modal frequency and damping ratio in the radial direction are concentrated in the ranges of 0.308~0.315 Hz and 2.75%~3.5%, respectively. The wind load is the key control one for vibration characteristics of the wind power structures. There is a negative correlation between the modal frequency and the wind speed, and a positive correlation between the modal radial damping ratio and the wind speed. With the increase of the wind speed, the correlation coefficient increases slightly when the wind speed is greater than 7 m/s. The modal frequency shows a certain degree of degradation, and the degradation is mainly concentrated in the first 150 days of the test period, reflecting the decline in the constraint effects of the soil on the bucket foundation. The weakening of the foundation-soil contact effects is the main reason for the degradation of the modal frequency, and the corresponding explanation and discussion are made by the stiffness weakening effects of foundation-soil contact and the scouring effects.