The adsorption behaviors of five imidazoline corrosion inhibitors with different alkyl chain lengths on a Fe(001) surface were investigated by molecular dynamics simulation method, and the inhibition mechanism was also discussed in depth. The results demonstrate that the head group of the imidazoline molecule is attached to the metal surface while the alkyl chain deviates from the metal surface. Stable corrosion inhibitor molecule absorption is achieved by self-distortion. Additionally, the combination of corrosion inhibitor and metal surface strengthens with the elongation of the alkyl chain, and the density of the corrosion inhibitor monolayer also increases. As a result, the formed dense corrosion inhibitor monolayer efficiently restrains the diffusion of the corrosive media from the liquid phase to the metal surface, which delays its corrosion. A theoretical evaluation of the corrosion inhibition performance of five corrosion inhibitors agrees well with the experimental results.