The mitochondrial DNA cytochrome b (Cyt b) gene segments of 190 yellow catfishes (Pelteobagrus fulvidraco) from five river sections of Pearl river were amplified by PCR technique and sequenced.The complete sequence of the mitochondrial(mt) Cyt b gene of Pelteobagrus fulvidraco was 1

109bp in length. Sequence analysis indicated that there are 43 haplotypes in 190 individuals. The global haplotype diversity (H

d

) and nucleotide diversity (P

i

) was 0.848 57 and 0.048 17

respectively

indicating a pattern of high haplotype with low nucleotide diversity in the whole population

which indicated that the genetic diversity was a medium level. Sequence alignment performed by Clustal-X 1.81 and MEGA 5.0 softwares showed that AT content (55.1%) was significantly higher than GC content (44.8%) in these samples

and the base distribution was uniform.The genetic differentiation between Duyun and Zuojiang populations was the largest (F

st

=0.414 30) based on the molecular phylogenetic tree constructed by maximum likelihood method. The analysis of molecular variance (AMOVA) showed that the genetic variation was 75.23% merely presenting within populations rather than between populations，implying that geographical factors caused certain effects on genetic differentiation of Pelteobagrus fulvidraco. Results of neutral test showed that expansion was not happened among these five populations

therefore their population structures and quantities were relatively stable.