Abstract: Stability is a comprehensive indicator of community structure and function, and has been the focus of ecological research. To further understand the variation trend of the stability of volcanic rock mountain forest communities at  different succession stages, three typical forest communities at different succession stages (Platycladus orientalis and Quercus variabilis mixed forest, P. orientalis mixed forest, and Q. variabilis and Pistalia chinensis mixed forest) in a typical volcanic rock mountainous region of Jiangsu Province, East China were taken as the study objects, four indicators (population regeneration, species diversity, Gordon stability value, and community structure) and eleven factors were chosen as the parameters to build an evaluation model, aimed to evaluate the stability of the communities by using the membership function values. With the development of succession, the stability of the forest communities was increasing, which was in line with the traditional succession theory, namely, the succession was from unstable to stable. Though the overall richness index and Whittaker’s diversity index of the three communities had definite differences, the two indices presented the same variation trend, i.e., P. orientalis mixed forest > Q. variabilis and P. chinensis mixed forest > P. orientalis and Q. variabilis mixed forest. P. orientalis mixed forest had the highest diversity, while Q. variabilis and P. chinensis mixed forest had the highest stability, i.e., the diversity could not fully represent the stability. The density of P. orientalis and Q. variabilis mixed forest was too large, and thus, appropriate tending should be made to promote the positive succession of the forest.