By means of first-principles calculations based on the density-functional theory, we investigate the vacancy trappings prevent hydrogen damage in two dimension alpha-Cr2O3/alpha-Fe2O3 (0 0 0 1) interface structure. Our calculations show that H atoms prefer to occupy the unoccupied O atoms octahedral interstitial site (O-site) in the center of the interface structure without vacancy defect, weakening the cleavage strength of Fe and O atoms and decreasing the work function and stability of interface structure. To prevent hydrogen damage in this interface structure, we model three Fe, Cr and O vacancy defects in this interface structure, respectively. Fe and Cr vacancy defects with lower H binding energy and higher work function, are better hydrogen trappings compared to O vacancy. These results confirm the Fe and Cr vacancy defects are effective hydrogen trappings to prevent hydrogen damage for passive film of steel, which has significant practical implications.