Abstract:Species diversity of the medicinal plant community in the Qin-Ba Mountainous area of southern Shaanxi was investigated using the quadrat method. Results showed that medicinal plants were comprised of 105 families, 268 genera and 361 species, which included 7 species (belonging to 6 genera in 5 families) of gymnosperms, 344 species (belonging to 254 genera in 92 families) of angiosperms and 10 species (belonging to 8 genera in 7 families) of ferns. Families that included 1-5 genera and genera that included one species had an advantage in number and proportion. Changes in species diversity of the vegetation types exhibited unique characteristics in the area. The species richness index (S), Shannon-Wiener diversity index (H), and Simpson diversity index (D) followed the order (from lowest to highest) of tree layer < shrub layer < herbaceous layer. However, changes in the Pielou species evenness index (J) were more complex. Species richness of the medicinal plant community in the tree layer and herbaceous layer first increased and then decreased with increasing altitude. The maximum value of species richness was at 1000-1200 m asl, namely between the evergreen broad-leaved forest and temperate theropencedrymion. Species richness of the shrub layer had no correlation to altitude, as determined by parabolic equation fitting. This research will provide basic data for illustrating the distribution pattern of plant species diversity in the mountainous region of Qin-Ba, and provide a theoretical reference for protecting and managing medicinal plants in the region.