The application effect of air-side economizer is closely related to outdoor air temperature, humidity and cleanliness, leading to significant variations in different regions. In this paper, the key factors affecting the applicability of air-side economizers were analyzed in terms of energy-saving potential and corrosion risk, and their assessment criteria were screened out. Then the K-mean cluster analysis was performed on zoning indicators from assessment criteria, and two zoning results were obtained, both of which could divide the country into eight climate zones. To determine a more reasonable zoning result, the consistency between available hours with different counting methods and energy-saving potential, as well as the effect of humidification energy consumption on energy-saving potential was discussed through energy consumption analysis. We conclude that the humidification method has a significant impact on the energy consumption and zoning results of the air-side economizer. When adopting isenthalpic humidification, it is more appropriate to assess the energy-saving potential of the air-side economizer by the annual available hours with DBTout ≤ 27 °C and DPTout ≤ 15 °C. Additionally, the zoning result obtained with this and pollutant concentration indicators is more reasonable. In the zoning results, Zone I is most suitable for applying air-side economizers due to its large energy-saving potential and low corrosion risk, but only includes Lhasa. However, Zone VII and Zone VIII are deemed to have high corrosion risk, resulting in higher costs for risk control in these areas, which comprise Taiyuan, Urumqi, Xi’an, Zhengzhou, Tianjin, Jinan and Shijiazhuang.