【Background】The sweet potato whitefly, Bemisia tabaciGennadius, is one of the most important pests worldwide, and has caused serious damage to agriculture production in China. Plant secondary metabolites may significantly affect the activity of several enzymes involved in detoxification, including carboxylesterase (CarE), glutathione-S-transferase (GSTs) and acetylcholinesterase (AChE) in B.tabaci. 【Method】The effects of capsaicin on activities of CarE, GSTs and AChE in B.tabaci were tested by conventional biochemical methods. 【Result】After exposed to 500 mg·L-1 capsaicin; CarE was activated at 6 h, but was inhibited at other times when the capsaicin concentration was increaed to 1000 mg·L-1, the activity was inhibited at 6 h, 12 h and 48 h, but was activated at other times; at 2000 mg·L-1, the activity was inhibited at 6 h, but was activated at other times. Treatment with 4000 mg·L-1capsaicin caused inhibition at 3 h and 12 h, but activation at other times; at 8000 mg·L-1, the enzyme was activated at 1 h, but inhibited at other times. At a concentration of 8000 mg·L-1, the activity of GSTs was inhibited significantly at 24 h and 48 h, but was activated at other times and other concentrations. In the case of AchE, the activity inhibition happened at 48 h after every concentration of capsaicin application. 【Conclusion and significance】The capsaicin may significantly affect the enzyme activities of CarE, GSTs and AChE in B.tabaciwith the dose or timedependent effects. This study could provide a basis for capsaicin application against B.tabaci.