Hot-dip galvanizing is the most economical way to improve the corrosion resistance of advanced high strength automobile steel. With the high trend of developing of automobile steel towards light-weight and high-strength, the contents of Si, Mn, Al alloy elements in steel increase accordingly. These alloy elements would be selectively oxidized during hot-dip galvanizing process, which affect in turn the wettability of steel surface and form different interface microstructures. However, its effect on the mechanical behavior of steel has never been known as clear as desired. Base on this point, the thermodynamics of the surface oxide and its effect on the interface microstructure of three high-strength automobile steels were studied after the same hot-dip galvanizing treatment as well as their tensile fracture behavior under different deformation conditions was in situ analyzed. Combined with the microstructure analysis and thermodynamic calculation, it can be concluded that different compositions of steel would produce different kinds of oxide on its surface. When Mn₂SiO₄ and SiO₂ were formed as thermodynamic stable phases, it was difficult to form a continuous Fe₂Al₅Zn_0.4 inhibition layer at the interface, zinc liquid could penetrate into the iron substrate and then form the brittle phase ζ-FeZn₁₃, where the crack was easily to be obtained and expanded to the substrate, resulting in the decrease of mechanical properties. When MnO and Mn₂SiO₄ with a small amount were formed as thermodynamic stable phase, the Fe₂Al₅Zn_0.4 inhibition layer can be obtained. Under the tensile stress, this crack generated at the interface and extended to the zinc layer. So, the fracture of the experimental steel was mainly resulted from the failure of substrate. When MnO and FeO were formed as metastable phase, Fe, as formed by aluminothermic reduction during hot-dip galvanizing, would reacted with zinc liquid to form Γ-Fe₁₁Zn₄₀ phase in the zinc layer. The crack generated under the tensile stress and expanded in the zinc layer. Since the unreduced MnO layer at the interface exhibited a higher bonding strength with substrate, tensile fracture of the experimental steel was caused by the failure of substrate.