Chemosensory systems are considered to play an important role in host plant selection in herbivorous insects. However, few studies have focused on chemosensory proteins (CSPs) for aphid host-location mechanisms. The roles of CSPs in searching for different Poaceae species (wheat, barley, triticale, maize and sorghum) were tested inRhopalosiphum padi, an important cereal pest. The olfactometer assays showed thatR. padiresponds to plant odors. SevenR. padi CSPgenes were identified. Influence of aphid morph, tissue and starvation state on expression patterns ofCSPswas evaluated. Expression levels ofCSP1,CSP4,CSP5andCSP6in winged aphids were significantly higher than those in wingless ones. Transcription levels of four genes (CSP1,CSP4,CSP5andCSP6) were relatively higher in the head with antennae, and the four genes tended to be upregulated following starvation. Silencing of threeCSPs (CSP4,CSP5andCSP6) altered aphid host-location behavior in response to the five different host plants tested. Three volatile compounds of host plants (octanal, [E]-2-hexenol and linalool) have significant attraction to wingedR. padiaccording to the four-arm olfactometer tests. Molecular docking predicted hydrogen bonding sites which played key roles in the binding of CSP4, CSP5 and CSP6 with volatile compounds. Knockdown ofCSP4orCSP5significantly decreased the staying time ofR. padiin the arms with octanal. However, knockdown ofCSP6could not affect the response ofR. padito octanal. These results bring evidence for the involvement of three CSPs inR. padihost-location behavior