Composition and content of corrosion products were analysed by X ray diffraction(XRD), and the microscopic model of corrosion products was established. Based on the molecular dynamics method, nanoindentation simulation was used to obtain the load displacement curve. The elastic modulus of the corrosion product was calculated. The results show that the corrosion products of steel bars in the concrete are formed by the heterogeneous mixing of four kinds of corrosion materials. The elastic modulus of the two groups of steel corrosion products with corrosion time of 6, 9d are 1609, 1633 GPa, respectively. The obtained result is in good agreement with the measured results in the existing literature. This simulation method can be used as a new method to determine the elastic modulus of steel corrosion products.