In order to study the indentation expansion law of the impact damage zone of the steel structure coatings under different impact heights and to analyze the elastoplastic characteristics of the steel structure coatings by calculating dynamic hardness and recovery coefficient the impact test of polyurethane coatings on steel structures was carried out with an automatic ball pressure impact meter The results show that the size of the indentation increases with the increase of the impact height. The indentation stress decreases first and then increases slightly with the increase of the indentation strain. The increase in the indentation stress indicates that the coating has basically lost its protective effect. The inside and edges of the indentation circumferential cracks， radial micro-cracks and long cracks are produced. The coating bulges within 2-3 mm from the end of the radial long crack. The dynamic hardness and recovery coefficient gradually decrease with the increase of impact height， and the coating's anti-deformation ability decreases.