Abstract: Adjusted mortality rates were used to measure the influences of secondary plant metabolites on Bacillus thuringiensis. Forty-eight hours after treatment, a significant difference (P＜0.01, One-Way ANOVA) was found among the mixtures of ethanol extracts and Bacillus thuringiensis (Bt). While the ethanol extracts of Zanthoxylum bungeanum, Duranta repens, Albizia falcataria, Bauhinia variegata, Psidium guajava and Magnolia grandiflora had synergistic effects on Bt, ethanol extracts of Ligustrum sinense, Ageratum conyzoides, Euphorbia pulcherrima, Nicotiana tabacum, Araucaria cunninghamii, Stellaria media, Bougainvillea glabra, Conyza canadensis and Kochia scoparia had antagonistic effect on Bt. There were no effects on Bt caused by the others.