Thermodynamic calculation on the smelting slag of direct recycling of electric arc face stainless steelmaking dust was presented. An induction face was used to simulate electric arc face smelting to recover the metals from the dust. The elements of iron, chromium and nickel in the ingot and the components of metal oxides in the slag were analyzed. The thermodynamic model for FeO-Cr2 O3-MgO-SiO2 slag was set up and the active concentrations of substances in the slag at 1 550 ℃C were determined by thermodynamic calculation according to the experimental data. The results show that the apparent equilibrium constant and quantitative distribution of chromium between slag and steel are unstable and affected by the mass ratios of pellets to start iron and metal reducing agent to the pellets. In order to get satisfactory chromium recovery from the direct recycling of electric arc face stainless steelmaking dust, it is important to ensure the mass ratio of pellets to the steel below 0.20 and the mass ratio of metal reducing agent to pellets over 0.18 in practical smelting runs.