Variable-freqair compressors are widely used in various fields of industrial production. This paper focuses on the modeling and the controller design of variable-frequency air compressors, where the model of a typical variable-frequency air compressor, containing a variable-frequency motor, a variable-frequency converter, and a pressure transmitter, is built. And then active disturbance rejection control (ADRC), with significant advantages in disturbance rejection, tracking and low dependence on precise mathematical models, is proposed for the variable-frequency air compressor. Simulation under conditions, such as user gas consumption constant condition, user gas consumption step change condition, user gas consumption step change condition and user gas consumption with uncertainties condition, are carried out. Simulation results show that ADRC can obtain satisfactory control performance for variable-frequency air compressors and broad application prospects.