The cotton bollworm, Helicoverpa armigera (Hü bner), is a wide host range pest that causes severe economic damages to agricultural crops in Iran and all around the world. During recent years, chemical insecticides have been used as the most effective strategy in control of this pest, but due to their hazardous effects, most of the researches are being conducted to offer an alternative approach for chemical control. In this regard, digestive systems, in particular inhibition of insect digestive enzymes, are considered as a target for pest control. Here, we used the original pro-region of H. armigera chymotrypsin as a potent and specific inhibitor of the pest enzyme. The structural model of the insect chymotrypsin was predicted based on homology modeling and the crystal structure of Bos taurus L. as template. The reliability of the model was assessed using VERIFY_3D, ERRAT, PROCHECK, WHAT-IF and Z-scores, and the results confirmed that the predicted structural model has an appropriate quality. Moreover, molecular docking simulations between the predicted structural model of enzyme and designed peptide showed that the inhibitor peptide has the most appropriate docking score and total binding energy for interactions with the insect chymotrypsin’ s active site. However, it showed a weak potential for interaction with Sus scrofa L. chymotrypsin, as a representative of the mammalian enzyme. The results of this report indicate the importance of computational studies in design and selection of the favored inhibitor pro-peptides against the target enzymes. Such inhibitors can be further suggested as a replacement of chemical pesticides for controlling of H. armigera as well as the other pests in future.