A new species belonging to the tribe Thalassaphorurini, Thalassaphorura problematica sp. n., is described from Northeast China. The new species is closest to the large genus Thalassaphorura by its simple vesicles in PAO and its furcal rudiment, but it does not fit the definition of the genus by the absence of chaeta d0 on head, the number of chaetae in the distal whorl of tibiotarsi and the labium type. We discuss the relative weakness of these last characters at generic level, which lead us to assign the new species to Thalassaphorura instead of erecting a new genus. The diagnosis of Thalassaphorura is broadened accordingly.