RNA interference(RNAi) is the method which controls phenotypes of gene in live cells. Chitinase is the enzyme helping digestion and absorption of old cuticles during the ecdysis of insects. In order to investigate molting-inhibition effect with the chitinase related gene in Spodoptera litura, RNA was extracted from the 5th instars. cDNA was synthesized and then we obtained about 645bp size chitinase. After PCR products were cloned into a pGEM T-easy vector, colonies were picked. DNA was extracted from the colony cultures. EcoR I enzyme was used to check whether PCR products were inserted or not. To synthesize the dsRNA, each DNA was cut with Spe I and Nco I enzymes. After synthesis, of dsRNA, approximately 5ul dsRNA was injected into the 3rd abdominal segment of S. litura 4th larvae. We confirmed insects that were phenotypically abnormal - for instance molting inhibition, change of integument color, malformation.