Abstract: The method of J. Moravec (1972) used to research the correlation between homotoneity and constancy of species has been applied to the steppe communities in the southern part of the Song-Nun Plain. The result shows a regularity of quantitative correlation of the species constancy in a community, frequently Ⅴ>Ⅳ⋛ Ⅲ< Ⅱ< Ⅰ. The homotoneity of releves is mainly dependent on the number of high-constancy species and their constancy per releve. From this relation, the homotoneity-coefficient of set of releves is calculated. The lowest value is 39.6% and the highest is 72.3%. By using these values and qualitative analysis, the steppe communities in the southern part of the Song-Nun Plain can be divided into 11 community types. The above is recommended as a simple quantitative method for classification of plant communities.