In order to reduce the energy consumption and maintenance cost of the equipment and improve the production efficiency, the "one control two" joint comprehensive control scheme of frequency conversion and energy saving is implemented for two different types of screw air compressors. The independent external frequency conversion control system is closely combined with the electrical control system of the original air compressor unit, and the frequency conversion and constant pressure gas supply are realized by combining PLC and frequency converter. The scheme is equipped with two sets of control loops in frequency conversion and power frequency state. The two systems can realize free switching, which can not only realize timesharing control, but also realize frequency conversion and power frequency dualmode switching, as well as two sets of equipment running at the same time, so as to realize the adjustment of gas supply in a large range. The comparative analysis and calculation results of the energy consumption before and after the transformation show that about 490000 degree electric of electricity can be saved each year, and the accumulated saving amount is more than 500000 yuan. According to the calculation of the number of production pieces, 0.07 degree electric of electricity can be saved for each piece, and the saving effect is obvious. The technical transformation of the frequency conversion joint control has a great promotion value and a certain reference value.