The impact of the wind environment on the deterioration of architectural heritage surfaces has often been underestimated. Wind acts directly on building surfaces, causing physical deterioration. This study focuses on the Nanjing City Wall in China as a case study. A full-scale 3D model of the city wall was established, and computational fluid dynamics (CFD) numerical simulation were used to quantify and evaluate the surface wind pressure of the city wall. Results showed that the presence of the city wall had a significant influence on the near-surface wind distribution characteristics. Even a small 22.5° variation in the dominant wind direction significantly altered the wind flow field. The windward surface of the wall was not consistently fixed to either the inner or outer surface. Small wind directional fluctuations could cause the windward side to alternate between the inner and outer surfaces of the city wall. The wind velocity primarily affected the surface wind pressure magnitude of the city wall, with a limited impact on its along-path distribution characteristics. Pressure polarity alternation (positive/negative reversal) might occur at locations with geometric configuration variations under changes of wind direction. This study provides an effective method for identifying the potential deteriorated regions of the city wall. To minimize the risk of wind-induced deterioration on the city wall surface as much as possible, protective measures such as planting windbreak belts at a certain distance from the city wall might be implemented.