Cylas formicarius is one of the most important pests of sweet potato worldwide, causing considerable ecological and economic damage. To improve the effect of comprehensive management and understanding of genetic mechanisms, the genetic functions of C. formicarius have been the subject of intensive study. Using Illumina and PacBio sequencing, we obtained a chromosome-level genome assembly of adult weevils from lines inbred for 15 generations. The high-quality assembly obtained had a size of 338.84 Mb, with contig and scaffold N50 values of 14.97 Mb and 34.23 Mb, respectively. In total, 157.51 Mb of repeat sequences and 11,907 protein-coding genes were predicted. A total of 337.06 Mb of genomic sequences was located on the 11 chromosomes, and the sequence length that could be used to determine the sequence and direction accounted for 99.03% of the total length of the associated chromosome. Comparative genomic analysis showed that C. formicarius was sister to Dendroctonus ponderosae, and C. formicarius diverged from D. ponderosae approximately 138.89 million years ago (Mya). Many important gene families that were expanded in the C. formicarius genome were involved in the chemosensory system. In an in-depth study, the binding assay results indicated that CforOBP4-6 had strong binding affinities for sex pheromones and other ligands. Overall, the high-quality C. formicarius genome provides a valuable resource to reveal the molecular ecological basis, genetic mechanism and evolutionary process of major agricultural pests, deepen the understanding of environmental adaptability and apparent plasticity, and provide new ideas and new technologies for ecologically sustainable pest control.