Abstract: The results of our investigations and analyses have shown that topographical, geomorphologic, hydrological, climatic and pedological conditions in the Song-Nen Plain all have potential effects on the formation of saline-alkali plant communities. Human activities such as overgrazing could bring about the degradation of Aneurolepidium chinenses grassland, as indicated by the appearance of saline-alkali plant communities. During the formation of saline-alkali plant communities, the species composition and population dynamics of the original community will change. The changes of the soil properties include salt content and the composition of salt ions, pH, soil organic matter content and its associated properties. Finally, the saline-alkali plant species reach an dynamic equilibrium with their habitats. Weighted average index and community coefficient were employed as quantitative indices to quantify the changes of vegetation characteristics during the formation of saline-alkali plant communities.