Abstract: In this paper, under mild conditions, the steady-state models for large-scale industrial processes are obtained by using the step signals of set-points in the procedure of optimizing control, and the sufficient conditions are obtained. The identification technique has advances of high accurately simple count, and less interference to the indusrical processes, as well as less information transmission with contrast to classical identification techniques.The validity and practicabity of this complete decentralized identification are demonstrated by sedation results.