Abstract Pheromone‐binding proteins ( PBP s) play important roles in the information exchange between insect sexes, specifically in the process of transporting fat‐soluble odour molecules from the external environment to olfactory receptors through the olfactory sensillum lymph. The PBP functions in this process may explain the sex pheromone identification mechanism used by insects, laying a theoretical foundation for the prevention and control of pests by interfering with olfactory recognition. In the present study, a PBP gene of Cyrtotrachelus buqueti ( G en B ank accession number: KU 845733) is cloned for prokaryotic expression. Using N ‐phenyl‐1‐naphthylamine as the fluorescent probe in a competitive binding assay, the ability of CbuqPBP 1 to bind 12 sex pheromone analogues and three volatiles of Neosinocalamus affinis shoots is examined. Of the 12 C. buqueti sex pheromone analogues, dibutyl phthalate gives the greatest displacement (inhibitory constant value of 11.1 μ m ), whereas the other sex pheromone components show much smaller displacements. Consistent with other PBP s, the three plant volatiles (linalool, benzaldehyde and indole) show only a limited displacement of CbuqPBP 1. However, the binding abilities of 1 : 1 ratios of each of the three plant volatiles with dibutyl phthalate show increases of 62.3%, 65.1% and 51.7% over the binding abilities of the three plant volatiles alone. CbuqPBP 1 has dual roles in the processes of sensing sex pheromones and plant volatiles.