Natural karst forests have long been degraded due to human disturbances in mountainous regions of south-west China. We analysed the woody species diversity, floristic composition and stand structure of subtropical karst forests in Maolan, Guizhou Province of southwestern China. A census of all woody species with diameter at breast height ≥ 1 cm in two 1-ha plots was made. A total of 8138 individuals belonging to 278 species, 167 genera and 69 families were recorded in the two plots. The most ecologically significant families as determined by stem density were Lauraceae, Fagaceae and Juglandaceae. The tree species Platycarya longipes (Juglandaceae) was the most dominant species in Dongge plot and Castanopsis carlesii var. spinulosa (Fagaceae), in Gengzheng plot. Total basal area was 42.22 m2 in the two plots, ranging from 18.60 to 23.62 m2 per plot. Forest structure was characterised by a large number of saplings. Compared with subtropical non-karst forests in China and karst forests in the tropics, the Maolan karst forest had higher species diversity with different tree species compositions. This study improved our understanding of the species diversity, community structure and functions of karst forests in subtropical Asia.