Abstract:Micro-morphological characters of Dioscorea in China,including shape of epidermis,feature of trichome hair,type and size of stomata,ornamentation of periclinal wall,and so on,was observed and measured using scanning electronic microscope (SEM),to provide foundation for taxonomic delimitation and phylogenetic study of Dioscorea.The results show that there are significant differences in trichome hair,epidermis and stomata among sections of Dioscorea.However,each section has its special feature.Such as quadrilateral or hexagon of epidermis and straight type of anticlinal wall in Sect.Stenophora.D.esculenta which belongs to Sect.Combilium covers a lot of T type binary trichome on vein and mesophll.Sect.Botryosicyos are with density trichome hair and tricytic stomata in Sect.Enantiophyllum.Stomatal orientation is left in Sect.Combilium,Sect.Lasiophyton and Sect.Enantiophyllum except D.decipiens.However it is right in Sect.Opsophyton,Sect.Botryosicyos and Sect.Shannicorea.The results indicate that micro-morphological characters of Dioscorea are relatively stable,which could be used as classification and identification of this genus in China.As a result,we conduct that Sect.Shannicorea and Sect.Enantiophyllum are more evolutionary,while Sect.Stenophora is center of variation of Dioscorea.The taxonomic treatments of controversial species were discussed at last,such as,D.zingiberensis,D.sinoparviflora,D.nipponica ssp.nipponica,D.nipponica ssp.rosthornii,D.simulans,D.decipiens and D.hispida.