7 329 sequences of snake cytochrome b gene(Cytb) were downloaded from GenBank database of NCBI and compared and pruned according to MT765098.1 sequence. We obtained 4 665 snake Cytb sequences, and calculated the nucleotide saturation, genetic diversity, and intraspecific and interspecific genetic distance of Cytb sequences to construct phylogenetic trees. The results showed that, based on Kimura 2-Parameter model, the average intraspecific genetic distance of snakes was 3.3% and generally less than 6.7%. The average interspecific genetic distance is 19.96%, which is generally higher than 9.3%, indicating that there are great differences in genetic distance between species of snakes. According to the genetic distance between species, 23 subspecies of snakes were identified. Pareas and Hydrophis contain composites, and Atractus dunni, A. iridescen and A. occidentali are sister species.