Abstract: A total of 10 sample lots were selected on waste hillsides of dry valleys typical of the upper reaches of Minjiang River for study on stability of the plant communities on these hillsides by using indices, such as Whittaker β-diversity, overall interspecific association, niche width, niche overlap, and cross points between the species proposition lines and accumulation relative frequency lines. Results show that the altitudinal gradient in β-diversity of the plant communities is very low, indicating that the species succession rate is low; and that the overall interspecific association within the plant communities is significantly positive, indicating that the plant communities are in the steady growth phase; and that Selaginella pulvinata, Allium sikkimense and Carex lanceolat, the three dominant species, relatively higher in niche width, form co-dominant communities. At the same time, interspecific niche overlaps are widely found. The cross point between the species proposition line and accumulation relative frequency line is 11.13/80.