Abstract: In this paper, a steady state identification method of containing outliers detection, i.e., combining polynomial filtering steady state identification with the new 3δformula, is proposed for the process data containing outliers. In the proposed method, the length of filtering window is adaptively searched by means of the history data. And then, the outliers in the process data are filtered and replaced by using 3δ formula. Finally, by making polynomial filtering to the present data in the window, the curve that shows the characteristic of the data is obtained. Moreover, the stability of the process is decided according to the characteristic of curve. Both simulation experiment and real application show that the proposed method performs better than traditional methods, e.g., APF method.