[Objectives]  To investigate the effects of plant secondary metabolites on apoptosis in Spodoptera exigua, and investigate the potential of these compounds to control this pest. [Methods]  Artificial diets containing either 0.01% coumarin or 0.01% quercetin were fed to early 3rd instar S. exigua larvae. The control group was fed an artificial diet without plant secondary metabolites. The apoptosis rate of larval cells in each treatment group was determined by flow cytometry 24, 48, and 72 h after treatment. Caspase (Secaspase-1, Secaspase-5) activity and that of the inhibitor of apoptosis protein (IAP) were determined by enzyme-linked immunosorbent assay, and gene expression levels were measured using RT-qPCR. [Results]  The interaction between the two secondary metabolites and time after treatment significantly affected both the apoptosis rate, and the activity and expression of SeCaspase and SeIAP. The apoptosis rate, enzyme activity, and relative gene expression (SeCaspase-1, SeCaspase-5, and SeIAP) of larvae fed artificial diets containing either 0.01% coumarin or 0.01% quercetin were markedly higher than those of the control group, and the apoptosis rate of the coumarin treatment group was significantly higher than that of the quercetin treatment group. After 24 h, the SeCaspase (SeCaspase-1 and SeCaspase-5) activity and gene expression level of the coumarin treatment group were significantly higher than those of the quercetin treatment group, and the SeIAP gene expression level of the quercetin treatment group was significantly higher than that of the coumarin treatment group. [Conclusion]  Although both coumarin and quercetin promote apoptosis in S. exigua, the same amount of coumarin induces a higher rate of apoptosis than quercetin.