The aims of this work were to explore the types and distribution of spontaneous vegetation communities in the herb layer along the green belt of the Nanjing Ming City Wall， and to determine the main environmental factors affecting them. The overall aim of our research was to provide a theoretical basis for building a green ecological corridor along the Nanjing Ming City Wall and to strengthen the protection of the ecosystem on this structure. Thirty sampling sites along the green belt of the Nanjing Ming City Wall were investigated in a field survey. Using the species importance value as an index， species diversity characteristics were analyzed on the basis of the alpha diversity index. The unweighted pair-group method with arithmetic means and canonical correspondence analysis were used to analyze the composition and distribution of the communities， and to explore the relationships between environmental factors and the spontaneous vegetation communities in the studied herb layer. It was found that： 1） The species diversity index and evenness index of spontaneous vegetation in the herb layer were high， and the species distribution was uniform. 2） The main flora communities along the green belt of the Nanjing Ming City Wall were： Trachycarpus fortunei-Veronica hederifolia+Carex chinensis+Youngia japonica； Stellaria media+Corydalis edulis+Orychophragmus violaceus+Veronica persica； V. hederifolia+Lamium barbatum+S. media+C. edulis； Elymus kamoji+L. barbatum+O. violaceus+C. edulis； Trachelospermum jasminoides-E. kamoji+V. hederifolia+Solidago canadensis； Semiaquilegia adoxoides+S. media+L. barbatum+Galium spurium； T. jasminoides-L. barbatum+O. violaceus+Thladiantha nudiflora； Rubus hirsutus+T. jasminoides-Cyclosorus acuminatus+E. kamoji； L. barbatum+E. kamoji+Oplismenus undulatifolius+Carex breviculmis； T. jasminoides-L. barbatum+V. hederifolia+O. violaceus； Rosa multiflora+T. jasminoides+Campsis radicans-Rubia cordifolia.3） The results of the canonical correspondence analysis showed that canopy density， litter thickness， wall height， and wall orientation were the main environmental factors affecting the distribution of spontaneous vegetation communities in the herb layer along the green belt of the Nanjing Ming City Wall.