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One new species is added to the genus Sinocyclocheilus, the largest cyprinid genus in China and the largest cavefish genus in the world. Sinocyclocheilus gracilicaudatus sp. nov. is similar to S. donglanensis but differs to other congeners in hav-ing normal eyes and scaled body, curved lateral line with 59–64 lateral-line scale rows, half-hard dorsal fin spine, 8 gill rakers and 8 predorsal vertebrae. Compared to S. donglanensis, the new species has a longer and more narrow caudal pe-duncle (caudal peduncle length 21.3-22.7 % vs. 16.8–20.4 % of SL; caudal peduncle depth 10.5–12.0 % vs. 12.5–15.5 % of SL), smaller eyes (eye diameter 5.8–8.3 % vs. 6.5–10.9 % of SL) and longer barbels (maxillary barbel length 16.6–24.3% vs. 11.1–21.1 % of SL; rictal barbel length 19.5–21.6 % vs. 11.3–21.1 % of SL). The new species is distributed in a subter-ranean river, belonging to the Longjiang River system; S. donglanensis occurs in the Hongshuihe River system, a system separate from that where the former species occurs. Key words: Sinocyclocheilus, new species, cavefish, China China has a very rich species diversity of cavefish, with more than 90 troglobite and troglophile species (Romero, et al., 2009; Zhao & Zhang, 2006). Southwest China including Yunnan, Guangxi and Guizhou provinces is the main area of distribution of these cavefishes (Romero, et al., 2009). Typical a karst geology and environment, suitable climate and hydrological condition, and a complicated hypogean water system, are the primary factor