This work is a biostratigraphic study on the upper part of the Lower Paleozoic Choseon Supergroup (Maggol Limestone, Jigunsan Shale and Duwibong Limestone) exposed in the Jangseong-Dongjeom area, the Taebaeg City, Gangweondo, by means of conodont study. The condonts from the Maggol Limestone, the Jigunsan Shale and the Duwibong Limestone are classified systematically. Two new species Aurilobodus n. sp. and Drepanodus n. sp. are proposed in open nomenclature. Conodont biozones are also established in three formations of the study area. Biostratigraphically the fauna of upper part of the Maggol Limestone is correlated with upper Liangjiashan Formation – First Member of the Upper Machiakou Formation in North China, with late Arenigian to earliest Llanvirnian in Europe, and with the fauna 2, 3 to some lower four of the North American Midcontinent conodont fauna. The fauna of the Jigunsan Shale is correlated with middle part of the Upper Machiakou Formation in North China, with Middle Llanvirnian in Europe and the fauna 4 of the North American Midcontinent. The fauna of the Duwibong Limestone corresponds to upper part of the Upper Machiakou Formation in North China, to late Llanvirnian to early Llandeilian in Europe and to the fauna 5 to 6 of the North American Midcontinent. Bioprovincially the Maggol and Duwibong conodont fauna are closely related to those of North China and the North American Midcontinent, while the Jigunsan Shale has a mixed nature of the North Atlantic and the North American Midcontinent. Finally, it is also confirmed that the lithostratigraphic tripartite division, namely the Maggol Limestone, the Jigunsan Shale and the Duwibong Limestone is reasonable.