Abstract: A skull of Hipparion (Proboscidipparion) sinense is reported from the Longdan locality in Dongxiang, Gansu Province, northwestern China. The previously known material of H. (P.) sinensein the Early Pleistocene Longdan fauna was only a Metacarpal III. The discovery of this skull not only confirms the specific identification of Hipparion in this fauna, but also increases the understanding of the cranial and dental characters of this species. The holotype specimen of H. sinense belongs to a senile individual, and no other complete skull of this species has been found. As a result, the new material from Longdan provides more key information for the diagnoses of H. sinense, and the structure of the nasal notch of this species becomes clear. The lower part of the nasal bone is a tenuous strip that extends far forward, comprises the posterior part of the lower margin of the nasal notch, and has a sharp anterior end reaching the level of the P2/P3 boundary, at a 30 mm distance from the posterior end of the nasal process of the premaxillary bone. The recognition of these characters is of great interest in determining the phylogenetic relationship of Proboscidipparion.