The mitochondrial cytochrome oxidase II (Co II) from four different apterygotensCryptopygus nanjiensis (Collembola),Neanura latior (Collembola),Gracilentulus maijiawensis (Protura) andLepidocampa weberi (Diplura) were sequenced. Their A+T content, number of nucleotide substitutions, TV/TV ratio, and Tamura-Nei's distance were calculated. A series of phylogenetic trees were constructed by parsimony and distance methods using a crustaceanArtemia franciscana as outgroup. Finally the evolutionary trend A+T content of CO II genetic divergence and phylogenetic relationship of apterygotan groups were discussed.