Abstract: In the propene ammoxidation reaction of acrylonitrile unit, feed mole ratio for propene and air is essential for improving conversion rate of propene and yield of acrylonitrile. Thus, refineries realize efficient and reasonable utilization of energy. In this paper, the steam consumption of air compressor group was analyzed for acrylonitrile unit. In order to obtain coupling relationship between steam consumption and variation of the process parameters pressure, flow, rotate speed, axis power at off design conditions, the mathematical models of turbine and centrifugal compressor were analyzed. The characteristic curve of air compressor was obtained by applying similar principle. The results show the trend of steam consumption with adjusting rotate speed and atmospheric valve. It provides reference for reducing running cost of air compressor.