Abstract: A numerical model for morphological evolution of high-temperature oxide scales of high-purity ferritic stainless steel at large scales was developed by coupling nucleation and growth thermodynamics-kinetics of Cr₂O₃ and cellular automaton model. The rationality and accuracy of the proposed model were verified by comparison with experimental results reported in literatures. The microstructure evolution and dynamics behaviors of high-temperature oxidation for high-purity Fe-Cr alloys were simulated by using the model, the effect of Cr content on the high-temperature oxidation kinetics of the high-purity Fe-Cr alloys was investigated. It demonstrates that the high-temperature oxidation process can be divided into three stages before the stable growth of oxide layer, including the initial nucleation stage of metal oxides, the stage of competition between rapid growth of oxide particles and elemental diffusion and the stage of slow formation of dense oxide layers. Finally, the density and thickness of the high-temperature oxide layer formed on the surface of the stainless steel exhibit a severe inhomogeneous distribution along the longitudinal direction. When the Cr content is lower than 29.0 wt%, the growth rate of the interface front of oxides increases gradually with the increase of time and remains stable eventually. When the Cr content is higher than 29.0 wt%, the growth rate of the interface front of oxides firstly reaches its maximum with the increase of time, then decreases gradually and levels off finally.