对江豚(Neophocaena phocaenoides) mtDNA的Cyt b（377 bp）和D-loop（343 bp）片段进行了测序和分析，并与GenBank中鼠豚类及一角鲸类同源序列进行了比较。研究结果表明，Cyt b基因片段的碱基组成平均为T：29.0%，C：28.8%，A：27.2%，G：15.0%；D-loop片段的碱基组成平均为T：35.9%，C：21.8%，A：32.4%，G：9.9%。Cyt b基因片段共出现109个变异位点，简约信息位点107个，序列变异度为28.9%，碱基替代主要发生在密码子第3位点上，转换/颠换为13.3；D-loop片段共有109个变异位点，简约信息位点100个，序列变异度为31.8%，转换/颠换为2.4。构建的系统发育树显示，江豚是鼠豚科中较早分化出来的一个类群，与一角鲸科的亲缘关系最近。2个片段序列的分析结果一致，棘鳍鼠海豚Phocoena spinipinnis、太平洋鼠海豚P. sinus和黑眶鼠海豚Australophocaena dioptrica聚为一支。
The nucleotide composition and phylogenetic relationship among the species of Phocoenidae and Monodontieae were studied based on the 377 bp sequences of Cyt b gene and the 330 bp sequences of control region (D-loop). For the Cyt b gene, the average nucleotide contents of T, C, A, and G were 29.0%, 28.8%, 27.2% and 15.0%, respectively; it had 109 variable sites, among which 107 were parsimony-informative, with a sequence variability of 28.9%;two singletons and nucleotide substitution mostly occurred at the third position and the transformation was 13.3. For D-loop fragment, the average nucleotide T, C, A and G contents were 35.9%, 21.8%, 32.4% and 9.9%, respectively; 109 variable sites were detected across the eight species, among which 100were parsimony-informative; the sequence variability was 31.8% and the transformationwas 2.4. The phylogenetic trees showed that Neophocaena phocaenoides represented the most basal member of the family, having a most intimate affinity to Monodontieae. The resultsalso indicatedthat the relationships among the taxa Phocoena sinus, P.spinipinnis and Australophocaena dioptrica were intimate.