A method of EIS measure-polarization-relaxation was used to investigate the corrosion performance of different hot-dip coating layers of galvanized steel. The result showed that the corrosion of hot dip galvanized steel was divided into four phases, and the corrosion of each phase was corresponded to different layer respectively. The anti-corrosion difference of every layer was very distinct. The optimal anti-corrosion layer of hot dip galvanized steel was δ phase. This method could be used to detect coating corrosion quickly.