Abstract: Based on the plane assumption of an elastic body joint surface, this study establishes a force model for the flange bolt group of a wind turbine, and combines the idea of sliding interpolation to calculate the axial force of the entire circle of bolts from the limited measured points. According to the relative stiffness characteristics of the bolts, proposed is a loosening detection method that is based on the asymmetry index. Under the condition of a small sample point layout, it realizes the non-blind area loosening positioning and loosening degree assessment of the entire circle of bolts at the flange of the wind turbine. Through the comparison between the data from the finite element simulation and the data from field measurement, the high accuracy and practicability of the proposed estimation model and loosening detection method are verified. Simultaneously explores the influence of the layout of measurement points on the accuracy of the estimation model and detection method, and presents a method for selecting the spacing of measurement points to ensure the accuracy of the estimation model.