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. To clarify the influence mechanism of this tolerance on tower reliability, this study established a high-precision finite element model of a 2 MW typical wind turbine that incorporates detailed flange structural features. 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.