The thermodynamic database of the Fe-C-Mn-Si system has been developed in the framework of the CALPHAD approach.The sub-ternary systems have been carefully evaluated and revised based on available experimental data.A satisfactory description of the liquid phase in the Fe-C-Si system has been obtained.The C-Mn-Si system was as-sessed treating the liquid phase as a substitutional solution.Phase equilibria in the C-Mn-Si system, especially those involving the liquid phase, can be well described.Based on the extrapolation of the experimental data in the quaternary system, the Fe-Mn-Si system has been modified to agree well with experimental data at high temperatures. The comparison between the calculated and measured phase transformation tempera-tures confirms the reliability of the present quaternary database.Additionally, the so-lidification process of Fe-0.16C-1.5Mn-1.5Si (wt.%) alloy was simulated by using the thermodynamic database developed.