Abstract: Northwest China possesses abundant wind energy resources, and wind power construction has expanded rapidly. However, the region is exposed to frequent wind-blown sand and saline-alkali environments, where erosion-induced cumulative corrosion has become a key factor restricting the service safety of wind turbine towers. Most existing studies focus on short-term wind-sand loads while neglecting corrosion arising from coating loss. Moreover, simplified models fail to capture operational conditions, and the absence of key mechanisms leads to insufficient accuracy in fatigue performance evaluation. To overcome these limitations, a comprehensive method is proposed to systematically assess the long-term service performance of wind turbine towers under coupled erosion-corrosion effects. The total coating loss under various wind-sand conditions is quantified using Bitter’s theory, and a damage mass redistribution criterion is introduced based on the tower wake and a Random-function algorithm to allocate corrosion-induced damage. A year-by-year iterative rotational model is established to quantify the coupling between corrosion accumulation and centrifugal stiffening. Corrosion models corresponding to different service years are incorporated into a full-element fatigue life assessment framework, and wind-induced fatigue analysis is performed to reveal the evolution of structural performance under complex environments. Results show that coating loss is more severe in non-wake zones; both wake and non-wake zones suffer localized fatigue damage, with the latter being more pronounced; and cumulative corrosion significantly reduces both hazard resistance and fatigue performance.