Zacco tiaoxiensis, a new species of cyprinid fish from Tiaoxi river system in Zhejiang Province, southern China, is described. With morphological comparison, the new species is similar to Z. acanthogenys, which is widely distributed in Zhejiang Province. However, the new species could be distinguished from Z. acanthogenys by the following combination of characters: lateral- line scales comprising 41 ~ 44 (vs. 44 ~ 47); scales above lateral-line 8 (vs. 8 ~ 10); scales below lateral-line 3 ~ 4 (vs. 4 ~ 5); scales surrounding caudal peduncle 12~15 (vs. 14~17); for mature male individuals, the ventral fin reaching (vs. exceeding) the anus, etc. The morphological differences among the new species and the allopatric congener species of Z. sinensis and Z. platypus are mainly in the number of scales under the lateral line, comparable characters such as the ratio of head length to body length, and the color of the upper edge of the eyes during living. Moreover, the genetic analysis based on mitochondrial cytochrome b gene also supports that the Zacco tiaoxiensis sp. nov. is a valid species.