Abstract: To realize the online monitoring and energy-saving evaluation of the fan energy efficiency on-site, an online detection system for fan energy efficiency suitable for field use has been developed based on Java programming language and industrial wireless data communication technology, in accordance with GB/T 15913, GB/T 10178, GB/T 34867.1 and other standards, which can realize the real-time monitoring of the unit consumption, motor load rate, and energy utilization efficiency, as well as energy saving monitoring, energy efficiency analysis and energy saving evaluation. By developing a fan verification platform to test the fan to be transformed, the results show that the system operates stably, and the detection data is accurate and reliable, which can reflect the operating condition and energy efficiency level of the fan in real-time.