Abstract: Abstract：The bioactivities of garlic extracts on Spodoptera litura and Bemisia tabaci in tobacco fields were determined by indoor and outdoor experiments. The results showed that antifeedant and toxic effects of the garlic extracts on S. litura larvae (3rd instar) were obvious, but the ones were week. However, it was very significant to deterrent or interfere B. tabaci by the extracts. Besides the concentration of 10 g?L-1 at 72h after the treatment was more poor, the others were very significant for B. tabaci during the experiment of deterrent. The rates of deterrent were between 69.44% and 100.00%. And the numbers of antifeedant rates were 54.83% and 68.63%, respectively. The ones of IIPC were 0.452 and 0.314, respectively.