Herein, the influence of cyclic planar molecular structure and linear molecular structure of polyaspartic ester polyurea amino component on the microstructure of polyurea coatings and the diffusion behavior of corrosive media within the coating was studied by means of molecular dynamics simulation. The results indicate that compared with linear molecular structures, cyclic planar molecular structures have greater steric hindrance, resulting larger free volume and lower density of the polyurea system; The increase in molecular branching can further increase the free volume of the coating, leading to a decrease in the density of the system; The increase in molecular chain segment length has a relatively small impact on the compactness of the system; Water molecules can form hydrogen bonds with polyurea molecules and tend to exist in an aggregated state inside the coating. Regarding the corrosion resistance of the formed coating, linear molecular structures are more conducive to formation of dense coating structures and enhancement of coating corrosion resistance. Finally, this article conducts a study on the correlation mechanism between coating structure and performance through molecular simulation methods, providing a new means of molecular simulation screening for coating formulation design.