This study was attempted to clarify the taxonomic problems that have been raised up to now in the study o section Telephium, genus, Sedum: the delimitation of taxa belong to Telephium group, their relationship, and nomenclatural confusion and the rank of Telephium group. Specimens were collected at 19 sites in Korea. The habitat, distribution, external morphological characters of habit, leaf shape, phyllotaxy, inflorescence, color of floral organs, floral formula, carpel, capsule, and micro-characters of pollen, seed coat, stigma and anther with SEM were examined. Through this study, the following results were obtained. The delimitation of taxa that belong to section Telephium in Korea and their relationship Nomenclatural errors were corrected. In S. rotundifolium Lee, species epithet“rotundifolium”is later homonym of s. rothundifolium Lamarck, so corrected to S. duckbongii Chung and Kim by article 64 of ICBN. Phyllotaxy was elucidated to meaningless, character in sect. Telephium. S. taquetii was a separate species from S. viridescens and not of its synonym. S. alboroseum Baker in Korea was S. erythrostictum sensu Master not of S. erythrostictum Miquel. By this study , taxa of sect. Telephium in Korea were arranged to 7 species. Considering interspecific relationship of sect. Telephium, S. duckbongii and S. alboroseum are considered to be more advanced forms and S. viridescens, S. taquetii, and S. viviparum to be more primitive forms among 7 species.