Abstract: By using the method of electrophoresis,three isozymes (lactate dehydrogenase,malate dehydrogenase and esterase) of three species of genus Gymnocypris were described and analyzed from North Tibet in this paper.The results showed that all three isozymes presented interspecific difference and distinct differentiation among individuals in the same population,and there was no electrophorectic difference between males and females.Analysis of relationships among three naked carps indicated a high degree of similarity between G.selincuoensis and G.cuoensis,whereas low degree between G.selincuoensis and G.namensis.Furthermore,three isozymes presented expression of null alleles,and the duplicate genes of LDH-A2,LDH-B2,s-MDH-A2 and m-MDH-B2 also expressed in some individuals.Compared to other tetraploid fishes,three naked carps retained more functional duplicate genes and null alleles.This suggests fishes of genus Gymnocypris are at the early stage of evolution after polyploidization than that of fishes of Catostomidae,it directly related to the later time of schizothoracine fishes originate as well as severe environment.