Abstract:The molecular phylogeny for Unicauda pelteobagrus Ma, 1998, isolated from Pelteobagrus fulvidraco in Ciqikou area of Jialing River, Chongqing China, was studied based on 18S rDNA sequences. The present work also first supplied the 18S rDNA sequences information of Unicauda pelteobagrus Ma, 1998. At the same time, the phylogenic relationship between U. pelteobagrus and U. caudatus was discussed inferred from the 18S rDNA sequences, genetic distance and the characteristics of the phylogenetic tree. The result indicates that U. caudatus has much closer phylogenetic relationship with Myxobolus caudatus and far away from U. pelteobagrus, which did not support the viewpoint that putting U. caudatus and U. pelteobagrus into the same genus Unicauda. The present study also revealed that the validity of genus Unicauda was questionable.