The traditional finite element analysis method in conjunction with the atomic simulation technology was applied to study the mechanical properties of nanostructure materials. A phase mixture model in which nanocrystalline material is regarded as a mixture of crystalline phases and intercrystalline phases (grain-boundary, triple line junction and quadratic node) and pores is presented. The Morse potential function was used to simulate the nonlinear constitutive model of grain boundary phase of NC Fe. The effects of grain size and porosity were investigated in the literature. The calculated results are compared with previously published experimental data.