Broussonetia papyrifera, Zanthoxylum bungeanum, Rosa roxburghii and Pyracantha fortuneana were selected as the adaptive plants for Karst Rocky Desertification in Southwest China. The fine root architecture and its correlation with the stoichiometric characteristics of C, N and P in fine root and rhizosphere soil were analyzed to explore the response of fine root architecture to rocky desertification and barren soil habitat. The results showed that the fine root architecture of B. papyrifera, Z. bungeanum, R. roxburghii and P. fortuneana tended to Herringbone branching, and the fine root topological indexes were 0.93, 0.95, 0.95 and 0.94, respectively. The fine root connection length of the four adaptive plants was longer, but the branching rate of fine root was smaller. The ratios of cross-section areas of the B. papyrifera and R. burejense before and after fine root branching were no significant difference with 1.04 and 1.03, respectively, which were consistent with Leonardo da Vinci's law. Fine root architecture was related to fine root and rhizosphere soil nutrients. The results of principal component analysis showed that the N content of fine roots and the stoichiometric ratio related to P in fine roots and rhizosphere soil were the main factors affecting fine root architecture. Further analysis showed that the four adaptive plants could obtain sufficient nutrients to cope with the changes of environment by reducing the secondary branches of fine roots, overlapping between roots and extending the length of fine root connection, so as to improve the nutrient absorption efficiency and ecological adaptability to karst environment. The results of the study have a certain scientific significance for revealing the adaptive strategies of fine roots of adaptive plants to karst rocky desertification habitat, and have obviously practical reference for vegetation restoration of Karst Rocky Desertification in Southwest China.