Abstract: The mechanism model of single stage compressor was built on the basis of the centrifugal compressor's characteristics, the fluid mechanics, the energy conservation and the mass conservation principles. Several models of single stage compressors in series were integrated to compose the mechanism model of a steel CCPP gas system's three-level centrifugal compressor on the low pressure side. The parameter identification problem of the multi-stage compressor model was transformed into an optimization problem, and differential evolution algorithm was used to decide the unknown parameters in the model. Model validation results showed that the developed model could reflect the operating characteristics of centrifugal compressors and laid a model foundation for compressors' anti-surge control.