In this study, the imagoes and subimagoes of Polyplocia orientalis Nguyen & Bae, 2003 (Ephemeroptera, Euthyplociidae) were reared from nymphs in the lab and described for the first time. Nymphal structures are also photographed and described. The imagoes of this species can be identified by having transparent wings (except costal and subcostal areas), sterna without regular markings and penis divergent in apical half and basal half fused. The K2P distance between newly-sequenced COI gene of Chinese materials and a stored Vietnamese one is 0.10. This report not only confirms the presence of the genus and family in China, but also provides the first nymph-imago association in the genus.