Mitochondrial DNA cytochrome b(Cyt b) gene was amplified by PCR and sequenced bidirectionally in Pingxiang Red-transparent Crucian Carp(Carassius auratus var.pingxiangnensis),a natural triploid Crucian Carp mutant in the area of Pingxiang City of Jiangxi Province.The results showed that there were no differences in sequences among the twelve samples.The gene sequence was 1 140 bp in full length which contained 28.2%(321),28.8%(328),14.8%(170),28.2%(321) of A,T,G,and C,respectively.The result of A+T(57%) > G+C(43%) was similar to that in other aquatic animals.The first codon evenly contained 4 nucleotides;the second codon had high content of T(41.8%) but low content of G(13.2%);the third codon contained 39.7% of A and 6.3% of G.The Cyt b gene of the Pingxiang Red-transparent Crucian Carp was proved to have high homology with other species of crucian carp recorded in the GenBank.The sequence similarity between this mutant crucian carp and the Silver Crucian Carp(C.a.gibelio) was 93%,and that between this mutant and Common Crucian Carp(C.carassius) was 98%.The result of phylogenetic tree constructed by Neighbor-Joining method indicated the closest phylogenetic relationship between the Pingxiang Red-transparent Crucian Carp and the Common Crucian Carp.