Abstract: Species diversity of Lachnum from tropical China was investigated. Four hundred and fifty one specimens of the genus were involved and they belong to 35 taxa. Of them, Lachnum abnorme var. abnorme , L. brasiliense , L. flavidulum , L. pteridophyllum , L. sclerotii and L. virgineum account for 73.4% of the specimens examined and are the most common species occurring in tropical China. The results indicate that species richness ( S =22) and diversity index ( H ′=2.6696) are highest in Hainan, and that species richness in Yunnan is the same as that in Guangxi. The coefficient of community ( cc ) was used to compare the floristic similarity of different areas. Impact of elevation, habitat, and substrate on species composition was also discussed. Within the 100～2000 m asl zone where the genus is found, three distribution patterns of Lachnum were identified: cosmopolitan, disjunct, and endemic.