Orthomnion wui T. J. Kop. is transferred to Plagiomnium T. J. Kop. (Mniaceae) as P. wui (T. J. Kop.) Y. J. Yi & S. He, based on the presence of well-defined stereid cells in its costa, a key character distinguishing Plagiomnium from Orthomnion Wilson. Originally described in 2007 from Hubei, China, O. wui is closely related to P. rostratum (Schrad.) T. J. Kop. but differs from the latter by enlarged juxtacostal cells, the thin-walled, almost undifferentiated epidermal cells of the dorsal costa and non-mammillate laminal cells. An updated key to the species of Plagiomnium in China is provided.