Abstract: According to the characteristics of wind turbine operation and the wind-induced fatigue damage of the embedded ring foundation,an online monitoring and damage assessment scheme of "upper and lower linkage,dynamic and static combination" is proposed. In other words,the installation position of the LVDT displacement sensor is determined based on the measurement results of the embedded ring levelness,and the displacement signals collected in real time are connected to the SCADA system of the wind turbine,which can realize synchronous acquisition,analysis and damage assessment with upper unit parameters. The field monitoring results show that the correlation coefficient between hub speed and embedded ring levelness is 0.8 or above under common working conditions such as start and stop,yaw,stable operation at high,medium and low speeds,which is extremely correlated. Therefore,it is feasible to regard the hubspeed as the "equivalent load on the foundation of the wind turbine. The fatigue damage degree of wind turbine foundation can be evaluated by drawing the curve of hub speed N-foundation ring displacement Δ and determining the curve parameters of critical hub speed,such as lower limit ndand upper limit nuand slope. By drawing the curveof the azimuth angle of wind turbine headθ and the maximum level of the embedded ring Δmax,the distribution area and size of the concrete wear cavity around the lower flange can be determined,which provides a clear reinforcement position for the later foundation grouting.