Abstract: 【Objective】This study aimed to investigate the insecticidal active components and mechanisms of Camellia oleifera Abel. cake against Mythimna separata， and to provide a reference for Mythimna separata control as well as comprehensive development and utilization of Camellia oleifera Abel. cake.【Method】The contact and stomach toxicities of petroleum ether， chloroform， ethyl acetate， and aqueous extracts of Camellia oleifera Abel.cake against third-instar larvae of Spodoptera frugiperda， Mythimna separata， Spodoptera litura， and Spodoptera exigua were evaluated by insect immersion and leaf immersion methods to screen extracts and test insects with the highest insecticidal effects. Insecticidal active compounds were identified through column chromatography isolation， insecticidal activity test and ¹H NMR and ¹³C NMR spectral analysis， combined with literature comparison. Furthermore， untargeted metabolomics technology was employed to annotate， screen， and analyze differential metabolites in the test insects.【Result】The petroleum ether extracts from Camellia oleifera Abel. cake exhibited the highest toxicity against Mythimna separata， with their median lethal concentration （LC₅₀） of 21.56， 15.11， 9.95， and 7.96 mg/mL on 1， 3， 5， and 7 d of treatment， respectively. Twenty-three fractions were isolated via silica gel column chromatography， among which the Fraction 4 showed the highest stomach toxicity against Mythimna separata， with LC₅₀ values of 37.41， 8.66， 5.50， and 4.06 mg/mL on 1， 3， 5， and 7 d of treatment， respectively. Further separation of the Fraction 4 produced 7 subfractions， with Fraction 4.1 displaying the highest stomach toxicity against Mythimna separata. ¹H NMR and ¹³C NMR analysis， along with literature comparison， identified Fraction 4.1 as triolein， with their LC₅₀ of 46.98， 9.15， 6.27， and 3.84 mg/mL on 1， 3， 5， and 7 d of treatment， respectively. Untargeted metabolomics analysis identified 143 differential metabolites， including 83 up-regulated and 60 down-regulated metabolites. Among the top 10 significantly differential metabolites， 5,6-indolequinone-2-carboxylic acid， pomalidomide， helenalin， mallotophenone， ligustilide， isotretinoin， decylubiquinone， and osthol were significantly up-regulated， while feruloylserotonin and ethyl myristate were significantly down-regulated. These differential metabolites were mainly enriched in seven signaling pathways： arachidonic acid metabolism， tryptophan metabolism， biosynthesis of various antibiotics， steroid hormone biosynthesis， betalain biosynthesis， biosynthesis of amino acids， and streptomycin biosynthesis.【Conclusion】The insecticidal compound in Camellia oleifera Abel. cake with insecticidal activity against Mthimna separata is triolein， which is potential to be developed as a novel botanical insecticide.