The Fe-Si system has been studied extensively due to its importance in steelmaking and electrical-magnetic applications. Thermodynamic and phase diagram data of the Fe-Si system available in the literature were critically evaluated and re-optimized to improve the thermodynamic description of this system. Two sets of optimized model parameters were obtained to reproduce the available and reliable literature data. In each set of parameters, the liquid phase was described using the modified quasi-chemical model or the Bragg-Williams random mixing model. The A2/B2 and B2/D03 order-disorder transitions were also taken into account in the present study.