In order to clarify the species of a cereal leaf beetle feed on spring wheat in Qinghe County, Xinjiang, China, the external morphology and internal reproductive organ structure of their adults were observed, and the mitochondrial COⅠ gene sequence and haplotype were also analyzed. The results showed that the body length of adult was 4.98~5.61 mm, with a dark blue head, 11-segmented black antennae, and an orange-red pronotum. Elytra were 3.44~3.67 mm in length, covered with 10 striae composed of dense and deep punctures. The femora (except base) and tibiae (except apex) were orange-red, while the remainder was black. The intromittent organ (flagellum) in male aedeagus is short, stout, and only slightly curved, with a length of 518.99 μm and a width of 86.29 μm. The ductus spermathecae is approximately 496.95 μm in length, with a heavily sclerotized proximal end, and coiled once. These external morphological features and genital structures are consistent with Oulema melanopus. Mitochondrial COI sequence analysis showed that the genetic distances compared to 11 other O. melanopus sequences from other countries ranged from 0~0.091, and the phylogenetic analysis also indicated that O. melanopus, O. mauroi, and O. duftschmidi were closest affinities. Haplotype analysis showed that this sequence belonged to one haplotype.