We identify one diatom species as Oricymba voronkinae Glushchenko, Kulikovskiy & Kociolek, which is reported for the first time in China, after examining the specimens collected from a headwater stream, which runs through the Jianghua Yao Autonomous County of Hunan province, by using light and scanning electron microscopy. The observation results demonstrate that O. voronkinae has the following diagnostic characteristics: (1) lanceolate valve outline with bluntly rounded ends; (2) valve face flat and clearly separated from the mantle by a marginal ridge; (3) grooves present along both sides of the marginal ridge; (4) the proximal raphe endings deflexed to ventral side, and the distal raphe endings bent to dorsal side at near a right angle, and a notch on the dorsal side of distal raphe fissure; (5) central stigma externally has single round opening, but internally has two slit-like openings occluded by fine ingrowths; (6) areolae are elongated slits, only the areolae near central axial area are semicircular to arcuate, partially occluded by dentate projections; (7) the undulate flap-like silica strips covering the internal apertures of each pervalvar row of foramina, not completely occluding internal apertures; (8) stria density 8–11/10 μm measured at the central valve part，areola density 25–30/10 μm. This study provides the accurate data of the areolae density and the detailed internal ultrastructure of the apical pore fields, which is not revealed in its original descriptions for O. voronkinae.