Culturally protected forests (CPFs), preserved and managed by local people on the basis of traditional practices and beliefs, have both social and ecological functions. We investigated plant species richness and diversity within the tree layer, shrub layer and herb layer in three types of CPFs (community forests, ancestral temple forests, cemetery forests) as well as nearby forests without cultural protection (NCPFs) in Southeast China. A total of 325 species belonging to 85 families and 187 genera were recorded in CPFs, including 17 protected species in China Species Red List and IUCN Red List, which accounted for 17 % of counties' endangered species. Compared with NCPFs, the tree layer of CPFs had larger DBH and lower species density, especially in the cemetery forests. CPFs had higher alpha diversity values generally, particularly in the tree layer. The differences in tree layer were substantial, and CPFs covered nearly 85.4 % of the tree species in the surveyed sites. The similarities between CPFs and NCPFs were higher in the herb and shrub layers than in the tree layer. These differences of species diversity may be attributed to differences in resource use and management between CPFs and NCPFs. Our field investigation results suggested that local CPFs harbor many plant species, high biodiversity, and contribute to the conservation of a substantial proportion of the local species pool.