Abstract: Self-weight as well as wind and wave loading cause the axial load and bending moment in the part of grouted connection of offshore wind turbine foundation. Due to the time variation of the wind and wave, stochastic direction and size of the loa, the turbine and its foundation will withstand load effects as many as 10⁹ cycles in the service period of 20 years or 25 years. Therefore, fatigue problem is severe. In this paper, the fatigue performance evaluation of steel structure, grouting material and integral structure is described, and then the fatigue mechanism of the connection with/without shear keys is studied. Finally, fatigue mechanism of grouted connection is summarized.