Seven common genetically stable sarcosaprophagous flies in three families and six genera were collected from large domestic pig carcasses placed in the field and cultured in the laboratory for many generations. The whole genome DNA was extracted and the COⅠ gene fragment was amplified. The forward and reverse sequencing was followed by splicing. The base composition of the amplified fragment and the rate of interspecific evolutionary divergence were analyzed by software such as Mega 7.0.26. The phylogenetic tree of COⅠ gene sequence of common necrophagous flies in the Yangtze River Delta was established by neighbor joining （NJ） method and unweighted pair-group method with arithmetic means （UPGMA） method.

The average base composition of different flies was A（30.14%）, T（38.23%）, C（15.98%）, G（15.65%）. The rate of interspecific evolutionary divergence ranged from 2.2% to 15.3%, the lowest rate was between Chrysomya megacephala and Chrysomya pinguis, the highest rate was between Muscina stabulans and Boettcherisca peregrina.

COⅠ gene can be used to identify the common necrophagous flies in the Yangtze River Delta.