Abstract: An investigation was conducted on the butterflies on the south slope of Taibai Mountain from April to October, 2009, with their diversity index, evenness index, dominance index, and species richness calculated and analyzed. A total of 126 species were recorded, belonging to 77 genera and 5 families. Nymphalidae had the highest diversity index (3.3621) and species richness (9.9363), and Pieridae had the highest dominance index (0.0573) and evenness index (0.8352). The genera and species were most abundant in June-August, the diversity index was the highest in July (3.4094), and the species richness was the highest in August (10.7). The biogeographic component analysis of 124 species (other 2 species were not identified) showed that the widely distributed species were most abundant (51 species), occupying 40.5% of the total, followed by Palaearctic species (41 species), occupying 32.5%, and Oriental species were the least (32 species), occupying 25.4%, which suggested that Taibai Mountain could be the transitional area of Palearctic and Oriental regions. The comparative analysis of the butterfly diversity and  faunal characteristics on the south and north slopes of Taibai Mountain showed that there were 85 shared species, and the similarity coefficient was 62.0%, indicating that the butterfly fauna had definite difference between the two slopes though they were geographically in proximity.