Toosendanin as one kind of plant pesticide exists in the fruits, barks, and leaves of Melia azedarach L. (chinaberry tree). To obtain toosendanin, the sample was defatted with petroleum ether, extracted with ethanol; then the solution was concentrated, and extracted with ethyl acetate. Uniform design and regression analysis were employed to establish a model of extraction and optimize the process. The results showed that the model was accurate to predict the toosendanin yield. Optimum extraction parameters were elicited as 1:24 g:ml for feed to solvent ratio and 20 min of extraction with petroleum ether, 1:34 g:ml for feed to solvent ratio and 390 min of extraction with ethanol, followed by extraction with ethanol:ethyl acetate (1:8, v:v) for 100 min. Under these optimal conditions, the yield was 0.74% of toosendanin on a dry weight basis. In addition, the toosendanin contents of the different part of chinaberry collected in different months for three years were analyzed. It was suggested that the toosendanin extraction from the leaves, fruits, and barks of chinaberry occurred in May and June, November and December, and June, November, and December, respectively. Thus, this study provides the direction for obtainment of toosendanin from chinaberry.