The samurai wasp, , is the predominant egg parasitoid of the brown marmorated stink bug, , in its native range in China. ()-2-Decenal is a major component of the alarm pheromone of , an important invasive insect pest with significant economic importance. . can be strongly repelled by ()-2-decenal, and thus its host location efficiency would be reduced in the field. Better understanding on the molecular basis of olfactory reception of this host alarm pheromone component by may provide opportunities to develop novel approaches to enhance biological control efficacy of the parasitoid against . We identified six Odorant Binding Proteins (OBPs) from by transcriptome sequencing, within which three classical OBPs were expressed in a heterologous expression system with , harvested, and then challenged with ()-2-decenal in binding assay experiments. OBP2 showed the highest binding ability to ()-2-decenal, compared to OBP1 and OBP3. Our results unambiguously suggest that OBP2 would play an important role in discriminating ()-2-decenal and could be a possible target for further intervention in the parasitoid-host system.