In order to define the combined effects of spinosad and plant allelochemicals on Helicoverpa armigera(Lepidoptera:Noctuvidae), the research fed them on artificial diets with different doses of spinosad, gossypol, quercetin and tannicacid, and the changes of pupal and imaginal biological characteristics were observed and recorded. The results showed that spinosad at sublethal concentrations decreased pupation ratio and pupal weight, prolonged prepupal and pupal periods, and decreased emergence ratio, fecundity and longevity of adults. Combined with plant allelochemicals, spinosad significantly prolonged pupal period and shorten adult longevity. Other life-cycle parameters such as pupation ratio, pupal weights, emergence ratio, eggs laid per female and hatch ratio did not change significantly. The results clearly indicated that plant allelochemicals did not change spinosad efficiency on H. armigera, but the combination of spinosad and plant allelochemicals might affect pest population dynamics significantly by changing its development. In order to define the combined effects of spinosad and plant allelochemicals on Helicoverpa armigera (Lepidoptera: Noctuvidae), the research fed them on artificial diets with different doses of spinosad, gossypol, quercetin and tannic acid, and the changes of pupal and imaginal biological characteristics were observed and recorded. The results showed that spinosad at sublethal pace decreased pupation ratio and pupal weight, prolonged prepupal and pupal periods, and decreased emergence ratio, fecundity and longevity of adults. Combined with plant allelochemicals, spinosad significantly prolonged pupal period and shorten adult longevity The results clearly indicated that plant allelochemicals did not change spinosad efficiency on H. armigera, but the combination of. spinosad and plant allelochemicals might affect pest population dy namics significantly by changing its development.