The beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), is a key pest of various agricultural crops in many countries throughout the world. The pest requires extensive use of pesticides and field-evolved resistances to conventional insecticides in China and other countries. Pinellia ternata Breit is native to the eastern part of Asia and foundmainly in China,which has been used in traditional Chinese medicines for N1000 years, but few studies have focused on the insecticidal activity of the P. ternate. In order to find natural products that could be used to control the pest in an safe, efficient and ecofriendlymanner,we first time analyzed the components of the anhydrous ethanolic extracts fromthe tubers of Pinellia ternate by using GC–MS method, and then investigated the insecticidal activities and biochemical mechanisms of the extracts against S. exigua. The result of GC–MS showed that 2-Methoxy-4-vinylphenolmay be an insecticidal active component, and we also found the extracts had notable insecticidal activity and disturbed the regular metabolismof S. exiguamainly through altering the activities of detoxification enzymes, digestive enzymes and protective enzymes. These properties suggest that the anhydrous ethanolic extracts from P. ternate can serve as a potential, efficient and ecofriendly S. exigua-control biopesticide.