University campuses, as small and isolated areas of rapidly growing urban areas, can provide a unique opportunity for urban biodiversity research, conservation, education, and citizen science by monitoring assemblages of butterflies within their areas. We surveyed butterfly biodiversity in a rapidly developing urban area represented by the Chenggong Campus of Yunnan University in southwestern China using the Pollard walk method. In total, 3625 butterfly individuals belonging to 50 species, 35 genera, and six families were recorded in this survey. The results showed that the families Pieridae and Nymphalidae are the families with the highest species richness on the campus, and that the family Riodinidae contained the fewest species. Pieris rapae was the most common species, and seven species assessed by the IUCN Red List were recorded. Butterfly community structure varied across habitats and seasons on campus, and butterfly diversity was higher in spring and autumn than it was in summer and winter, as well as being higher in road habitats than in scenic habitats. Unavoidable urbanisation activities (construction, green space planning, etc.) may have influenced the composition and diversity of butterflies, and conserving urban butterfly diversity requires a balance between urban planning and habitat diversity. Finally, we encourage universities and research institutions to develop butterfly monitoring platforms for citizen scientists to participate in.