By doing Erichsen experiments,samples of hot-dip galvanized sheet under different Erichsen depths (ED) were got.Surface and cross-section of these samples were analyzed by using SEM and EDS.Failure modes of galvanized sheet under different ED were researched.Then evolution process of zinc coating failure and effects of it on galvanized sheet formability were discussed.The results indicate that during galvanized sheet stamping,zinc coating will pulverize,exfoliate and fracture for influence of friction and forming force,which leads to decrease of galvanized sheet formability.