Abstract: The genus Sinocyclochei lus (Cypriniformes:Cyprinidae:Barbinae) is endemic to China and only found in Yunnan,Guizhou and Guangxi Provinces.The nuclear DNA content of two species and the ploidy level of three species in Sinocyclocheilus had been determined in the middle of 1980s.In recent years,more and more new species were reported in this genus.Therefore,it is necessary to analyze the nuclear DNA content,ploidy level and evolution of the species in the genus.In the present paper,by means of the red cell spreading-Feulgen staining-cytophotometry technique,we have measured the nuclear DNA content of 17 species in Sinocyclocheilus from Yunnan,Guizhou and Guangxi Provinces and distributed in the drainage of Nanpanjiang,Jinshajiang,Beipanjing,Yuanjiang,Hongshuihe and Youjiang rivers.The results showed that the nuclear DNA content of all 17 species were between 4.19 and 4.86 pg,as the same level of the related tetraploid species,doubled that of the related diploid species.It is likely that all of these 17 species and the whole genus Sinocyclocheilus have tetraploid origin.