Abstract: Stipa breviflora, Agropyron oristatum and Artemisia frigida Association widely distributes in Qilian Mountain. The method of Fuzzy Mathematic was used to study the division of grazing retrogressive succession stage of the Stipa Steppe. The Degree of Fuzzy in different succession stages are L(AⅠ) =0.3675, L(AⅡ) = 0.55745, L(AⅢ)=0.5831, L(AⅣ) = 0.49175 respectively. The following preliminary conclusions can be drawn by the study: 1. It is confident that using the method of Fuzzy Mathematic to study the stages of grazing retrogressive succession of the Stipa Steppe, one may divide the stages of succession quantitatively and correctly. 2. The result of division shows that degree of fuzzy in the first and last stages is small, yet, in the middle stages is rather big (that means their delimitation is not quite clear). Such a phenomenon may be a common rule in this type of retrogressive succession. 3. The conclusion of this paper confirms that the terms "critical stages" and "critical indicative Species" which the authors have given in the paper of “Mathematical Models of Retrogression of Population” under Grazing Condition in the Stipa Steppe "are valuable for the purpose".