Angiotensin-I converting enzyme (ACE) is a two-domain dipeptidylcarboxypeptidase involved in regulating blood pressure via the kallikrein-kininand renin-angiotensin-aldosterone complex. Therefore, ACE is a key drug target for the treatment of cardiovascular system diseases. At present many works are focus on searching for new inhibitory peptides of ACE to control the blood pressure. In order to exploit the interactions between ACE and its inhibitors, molecular dynamics simulations were used. The results showed that (a) the secondary structures of the three inhibitor-protein complexes did not change significantly; (b) root-mean-square deviation (RMSD), radius of gyration (Rg), and solvent-accessible surface area (SASA) values of Leu-Ile-Val-Thr (LIVT)-ACE complexes were significantly higher than that of other systems; (c) the backbone movement of LIVT was vigorous in Asp300-Val350, compared with that in Tyr-Leu-Val-Pro-His (YLVPH) and Tyr-Leu-Val-Arg(YLVR), as shown by the center-of-mass distance; and (d) the backbone movement of Asp300-Val350 may contribute to the interaction between ACE and its inhibitors. Our theoretical results will be helpful to further the design of specific inhibitors of ACE.