Abstract: To investigate the toppling failure mechanism of wind turbine foundation with colluvial soil as the bearing layer under wind load,a 2 MW circular expansion foundation was taken as the research object. Based on the ABAQUS finite element program,the foundation soil stress and foundation settlement of the interior 1∶10 scale model is carried out. In the meanwhile,the reliability of the numerical model is verified using the scale model test results. According to the results,the effect of random ground wind load on the expansion of stress and uneven settlement of foundation soil are the main reasons for the toppling failure of wind turbine foundation.When subjected to strong wind loads,the soil on the edge of the windward side foundation first enters plastic range. As a results,the yielding damage of the overlying soil cause the overlying soil to bulge,consequently leading to overturning of foundation. It is recommended that when calculating the basic design of a wind turbine,the settlement at the relative settlement check point on the central axis of the wind turbine foundation should be multiplied by a suitable settlement enlargement factor so as to ensure the safety and stability of the infrastructure.