【Background】Rotenone and tea saponin are typical botanical pesticides, but we have no information about their combined effect on palm pests. 【Method】The bio-assay method was used to detect the toxicity level and co-toxicity coefficient (CTC) of rotenone and tea saponin on the palm pest,Tirathaba rufivena. 【Result】The LC50 of rotenone and tea saponin on 3rd instar larvae of T. rufivena were 19.06 mg·L-1 and 35.07 mg·L-1, respectively. The rotenone mixed with tea saponin at proportions of 1∶1, 5∶1, 1∶2 and 1∶5 all showed synergistic effects to T. rufivena. The highest synergism was observed at a mixture of rotenone∶tea saponin at a ratio of 1∶5, with a CTC of 327.26, followed by a blend of 1∶2, with a CTC of 298.16. 【Conclusion and significance】Mixed at reasonable proportions, rotenone and tea saponin could express synergistic effects to T. rufivena.