With the aid of two methods of Fuzzy Clustering Analysis-Systematic Fuzzy Clustering Analysis and Interation Self-Organizing Data Classification (ISODATA), this paper divides the plant communities of the retrogressive succession of the Stipa Steppe. The results show that it is more successful and ideal to combine the Principal Component Analysis (PCA) with the ISODATA to classify the plant communities. Both methods of Fuzzy Clustering Analysis divide the reprogressive successional stages into four types. St...