Abstract: Cadherin was confirmed to be the receptor of Bacillus thuringiensis (Bt) insecticidal protein in several Lepidoptera insects.Cadherin gene in Plutella xylostella was silenced by RNAi technique and effect of cadherin gene silencing on susceptibility of P.xylostella larvae to Cry1Ac toxin was investigated.The results showed that the expression level of cadherin gene reduced from the first day to the fifth day after the dsRNA corresponding to cadherin segment was injected,and the most significant reduction was observed sharply at the second day.The susceptibility of resistant and susceptible strain of P.xylostella larvae to Cry1Ac toxin decreased after cadherin gene being silenced.The results suggested that cadherin gene was related to resistance of P.xylostella to Cry1Ac toxin.