In China, Acipenser ruthenus is considered to be naturally distributed in the Irtysh River, but there is no report on them, and whether it is distributed in the Irtysh River. We collected a sturgeon specimen in the lower reach of the Irtysh River (185 Corps) in northwest of China in September, 2019 (Fig. 1). The Body length of the specimen is 91.5 cm, the weight is 5 520 g; 11 dorsal scutes, 64 lateral scutes and 12 ventral scutes. Mouth ventrally situated and small, middle of the lower lip clearly slit and 17 gill rakers, which conforms to the morphological characteristics of A. ruthenus (Fig. 2). According to the phylogenetic and genetic distance analysis of 10 species of the genus Acipenser based on the mitochondrial Cyt b gene sequence (1 141 bp, Table 1), the results showed that the genetic distance of this specimen is the closest with A. ruthenus in Danube and Ob River (sequence divergence was 0﹣0.00 2), and they have gathered on one branch of the evolutionary tree, which should be intraspecific (Fig. 3). In summary, determined that this specimen is A. ruthenus, and the species was the first time discovered in the Irtysh River, and also a new record species of Acipenseriformes distributed in China. The specimen was preserved in the herbarium of fisheries in the Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences (Specimen No. 80092871).