An air compressor is a device that uses a motor to compress gas in a compression chamber and make the compressed gas have a certain pressure. It has a wide range of uses and can be used in various industries such as metallurgy, machinery manufacturing, mining, electric power, textile, petrochemical and so on. Air compressors account for 15% of the power consumption of large industrial equipment (fans, pumps, boilers, air compressors, etc.). After investigation, most air compressors have the following shortcomings: (1) When the output pressure is greater than a certain value, the load relief valve is automatically opened to make the asynchronous motor idle, which is a serious waste of energy. (2) The asynchronous motor is easy to start and stop frequently, which affects the service life of the motor. (3) Bad working conditions and loud noise. (4) The degree of automation is low, and the adjustment of the output pressure is realized by artificially adjusting the opening of the valve. The adjustment speed is slow, the fluctuation is large, the stability is unstable, and the precision is low. (5) The starting current of the power frequency of the air compressor is large, the impact on the power grid is large, the motor bearing wear is large, and the equipment maintenance is large. In view of the above problems, a frequency converter is designed to realize the energy-saving transformation scheme of the screw air compressor. After analysis, the scheme has a high degree of automation, significant energy-saving effect and good practicability.