In order to investigate the floristic composition and woody species diversity on the basis of architectural stratification in a subtropical evergreen broadleaf forest in Dinghushan Nature Reserve, South China, a 35 m × 35 m plot was established. The forest stand consisted of five architectural layers. Cryptocarya concinna Hance was the most dominant species with the highest importance value (20.7%). The relationship between the number of species and area did not show any regular trend among layers, but the bottom layer contained the highest potential number of species (126), which was almost the same as in the total stand (127). The floristic composition of the fourth and the bottom layers was almost similar on species, genus and family levels, and the top layer was almost exclusive from the lower four layers on genus and family levels. However, on a species level the top and the second layers as one group were almost exclusive from the lower three layers. The values of Shannon’s index of H′ and Pielou’s index of J′ were 3.01 bit and 0.48, respectively, for the total stand, and they tended to increase upward except H′ for the upper two layers.