Abstract: This paper examines the upgrade of cooling tower fan control systems in chiller units from traditional contactor-thermal relay control to variable frequency drive (VFD) control. It focuses on analysing the shortcomings of traditional control methods and elaborates on the energy-saving mechanisms and application advantages of VFDs in cooling towers. The study provides a detailed account of the implementation of the technical retrofit scheme and, drawing on practical case studies, conducts a comprehensive evaluation of the retrofit’s effectiveness across multiple dimensions, including energy saving and noise reduction. The results indicate that the application of variable frequency drives in cooling towers not only effectively reduces start-up noise but also promotes energy conservation and emission reduction, demonstrating significant economic and environmental benefits, and providing a practical reference for technological innovation in related fields.