The complete mitochondrial Cyt b gene sequences were analyzed to detect the diversity of Schizothorax biddulphi and Diptychus maculates.A total of 41 individuals of S.biddulphi were sampled from 3 localities(Simuhana,Yashi and Kalabeili) and 23 individuals of D.maculates were sampled from 1 locality(Simuhana) of Kezilesu River,West Xinjiang autonomous region.In S.biddulphi,6 variable sites were detected and 4 haplotypes were defined,which has low haplotype diversity(0.525 4) and low nucleotide diversity(0.001 16).Analysis of molecular variance(AMOVA) indicated that all of the genetic variations observed were found within three populations.The average Kimura 2-parameter distances among the three populations of S.biddulphi,the population differentiation values(F_st<0.085 25) and the level of gene flow(N_m>3.18) all showed that there was no genetic differentiation among these three populations,indicating that the three populations belong to a single population.In D.maculates,7 variable sites were detected and 8 haplotypes were defined,and the haplotype diversity and nucleotide diversity were 0.830 1 and 0.001 13,respectively.Both S.biddulphi and D.maculates have low genetic diversity,indicating their weak viability to maintain population.