In order to accurately evaluate the reliability of wind turbine yaw bearings under actual operating conditions, a modified Hertzian model that considers thermal-induced additional loads and was validated by thermal-mechanical coupled finite element simulation was used to investigate the characteristics of double-row four-point contact ball bearings under thermal-mechanical coupling.The results show that the relative error of the maximum contact stress between the modified model and the simulation is only 0.41%, which reduces the deviations caused by neglecting thermal deformation in traditional theories. Thermal-mechanical coupling increases the maximum contact stress. The increment decreases as the overturning moment rises and remains insensitive to the axial load.Analysis based on the Weibull wind speed distribution indicates that the theoretical life drops by 7.49% when considering thermal effects, compared to normal conditions. Non-uniform thermal expansion between components is the primary factor for stress elevation.It is concluded that neglecting thermal-mechanical coupling leads to overestimated reliability, and the proposed methods provide theoretical support for the precise design of yaw bearings.