Abstract: As a key connection part of the tower, the flatness tolerance generated in the manufacturing process of the flange is an important factor affecting the structural performance. In order to clarify the influence mechanism of this tolerance on the reliability of the tower, a high-precision finite element model integrating flange structural details was established for a 2 MW typical wind turbine. The influence of different flatness tolerances on the stress distribution of the tower under extreme gusts was systematically studied by means of static analysis and actual detection. This study provides a useful reference for optimizing the design of flange structure.