Abstract: Athetis lepigone (M-schler) is a new insect pest of summer corn in HuangHuaiHai Region of China. To understand the spread and damage of this insect pest in Shandong Province, we analyzed the genetic structure of the A. lepigone populations collected from 12 counties and one morphologically alike species from Weihai using mitochondrial cytochrome oxidase I (mtCOI, 608 bp) gene. The results showed that there were 24 mtCOI haplotypes generated from 130 sequences of A. lepigone and 2 haplotypes from 7 sequences of morphologically alike species of A. lepigone. The haplotype network and phylogenetic tree showed that the populations in the study formed two distinct groups, i.e., the population of Weihai (WH) and the other populations. The two groups were significantly differentiated and the genetic distance between them was 0.044-0.054. Molecular variance (AMOVA) analysis showed that a high proportion of the total genetic variance was attributed to variations among groups,  indicating that there was no obvious population expansion among A. lepigone populations   in this province. The study provided the scientific basis for the forecasting and prevention of the insect pest.