To analyze the regulation mechanism of AcMNPV (Autographa californica multicapsid nucleopolyhedrovirus)-mediated expression of BmK IT under IE1, P10 and PH promoters in the larva of Heliothis armigera.. The transcription level of BmK IT gene in midgut and epidermal tissue was analyzed by quantitative PCR. The start time of transcription of recombinant BmK IT gene was early under the regulation of IE promoter, whereas transcription of BmK IT was high under the regulation of P10 promoter in the midgut tissue of infected larvae. TdT-UTP nick-end labeling (TUNEL) assay showed the degree of apoptotic cell death in the midgut tissue of AcMNPV-BmK IT-transfected insect larvae was higher than that in the AcMNPV treatment group at 8 h post-infection. The time-effect relationship between the insect's humoral immunity and regulation of promoters was confirmed in the phenoloxidase activity assay. The anti-insect mechanism and regulation of different promoters in AcMNPV-BmK IT at molecular and cellular levels provide an experimental basis for the development of recombinant baculovirus biopesticides.