The simulated oxidation behavior between the rolling temperature and the rolled-in-scale of hot-rolled steel coils has been investigated over the temperature range of 850~1150℃. The relationship between the indoor rusting and the oxide scale of as-rolled steel coils has also been investigated. The methods included oxidation and rusting tests, microstructural analyses of oxide scales and the substrate, hardness and tensile testing, and the measurements of corrosion potential of as-rolled steels. The results showed that the higher the temperature, the more amount of Fe3O4, but the less amount of FeO present in the scales. The hardness ratio of the scales to the substrate also increased with increasing temperature, resulting in an easier increase the amount of rolled-in-scales during the rolling process. Concerning the oxide scales of the as-rolled steel coils, the more the pores in the scales, providing the shortcut of the corrosive species in the environments to diffuse through the scale and react with the substrate, the easier the point rusts could form in the scales.