The mitochondrion of animals is a organelle appearing in cytoplam of eukaryotes. According to the complete sequences that have been sequenced,it contains genes encoding 13 proteins,2 rRNAs,22 tRNAs and one major non-coding region(D-Loop).It is reported that a R-Loop structure has been found,with the characteristics of maternal inheritance,and the average evolution rate is 10 times faster than that of nuclear genome,especially D-Loop.The existence of tandemly repeat sequences in control region of mitochondria would be regarded as a special molecular marker in animals researches because of the interspecies and intraspecies differences.According to the structural and genetic characteristics of mtDNA,by means of advanced bioinformatics and rich databases,the researchers have made great progress in the field of molecular phylogenetics of animal populations,and make certain taxonomic status,interspecies and intraspecies relationship.