oxidase subunit I genes (CO I) were sequenced from 97 individuals out of 11 common species of Cephalopoda in China by using the universal barcoding primers. The 97 sequences were compared with the other 95 homologous sequences belonging to 19 species of Cephalopoda obtained from the GenBank. As a result, 23.33% of the Cephalopoda species’ COI sequences included Insert-Deletion sites. The indels of COI sequences in counted up to 33. The COI sequences of Cephalopoda present the base preference. On average, the content of A+T was significantly higher than that of G+C (33.30%). As calculated by Kimera-2-parameter model, the mean distance pairwise-species and within-species was 0.202 4 and 0.007 2, respectively. The valid name and taxonomy of swordtip squid ()remain controversial or unresolved. Here data gathered using COI genes does not support the assertion that swordtip squid In view of the fact that small genetic distance 00.0385) is found, suggesting that the threshold of barcodes (0.02) to identify species be worth furthering studies, particularly for those species with low genetic variation. According to maximum parsimony and neighbor joining trees for all 192 sequences of Cephalopoda, the consistency with morphological classification on both species and genus levels was much higher (100%, 91.67%) than that of family or order levels (80%, 66.67%). Consequently, providing essential revision and supplement to morphology taxonomy, the COI barcoding is a useful tool for both identification and phylogeny of Cephalopoda.