Thirty-seven ostracod species belonging to 25 genera from the Devonian-Carboniferous (D/C) transition in Dushan of Guizhou, South China are identified and figured. The stratigraphical distribution of ostracods in the Baihupo section suggests that the D/C boundary should be fixed in the basal part of the Tangbagou Formation, which is also the boundary between Gelaohe and Tangbagou formations. The ostracod assemblages from the Gelaohe Formation belong to the Eifelian Mega-Assemblage, incorporating palaeocopid and smooth-podocopid associations, which implies a nearshore-offshore palaeoenvironment, while the ecological assemblages of ostracods from the Tangbagou Formation correspond to a smooth-podocopid association that indicates an offshore palaeoenvironment. There was probably a transgression during the D/C transition when Gelaohe and Tangbagou formations were being deposited in Dushan of Guizhou.