A simulation model of the oxygen enriched bottom blowing for copper smelting was performed with ASPEN PLUS based on minimization of Gibbs free energy. The proposed model can well simulate each step of the oxygen enriched bottom blowing copper smelting process. It unravels the long-standing difficult problem of the smelting process that an effective theoretical model for the operation of metallurgy is lacked. The effectiveness of the model is proved by the simulation result which agrees appropriately with the actual production data from a smeltery. Moreover, the quantitative calculation with our model provides a workable way to analysis the viscosity of slag solves, and the influence of varied fuels can also be simulated quantitatively. The presented model can help to understand and research the copper smelting quantitatively and even can promote the smelting performance.