Dynamic mechanical properties of steel under the loading of blast and impact is always a concerned issue. Regarding Fe-C alloy, the basic composition of steel, as the research object, the uniaxial tensile deformation of Fe-C alloy at nine temperatures and four strain rates was analyzed using molecular dynamics (MD) simulations. In the research range, it was shown that the elastic modulus of Fe-C alloy is independent on strain rate, but sensitive to temperature, the elastic modulus decreases obviously with the increase of temperature; the yield strength and peak strain increase with the increase of the strain rate at the same temperature; the yield strength and peak strain decrease with the increase of temperature at the same strain rate; there is no interrelation between the temperature and strain rate effects of the yield strength. To provide evidence for the description of dynamic tensile mechanical properties of steel under the loading of blast and impact, the forecasting formula on dynamic tensile mechanical properties of Fe-C alloy affected by temperature and strain rate at nanometer scale was put forward based on the results of the simulation.