In this work, molecular dynamics simulations were employed to investigate the influence of inhibitor concentration on inhibition performance. The adsorption configuration, adsorption process, and inhibition performance were studied. We found that an ordered self-assembled inhibitor film can form on a metal surface, which plays a key role in corrosion inhibition. When the concentration reaches a critical value, inhibitor molecules organize into a micelle in aqueous solution. Further increasing the concentration did not change the inhibitor film on the metal surface, so that the inhibition efficiency remained at a constant level. Our analyses demonstrate that the number of water molecules displaced by inhibitor molecules, the diffusion of water molecules in the inhibitor film, and the stability of the inhibitor film play key roles in the process of corrosion inhibition. This work provides a thorough molecular-level understanding of inhibition behavior and the role of inhibitor concentration.